I verified the symbol it is not entered twice.

XML file for sale.order.form is given below

<?xml version="1.0"?>

<form string="Sales Order">

                    <header>

                        <button name="invoice_recreate" states="invoice_except" string="Recreate Invoice" groups="base.group_user"/>

                        <button name="invoice_corrected" states="invoice_except" string="Ignore Exception" groups="base.group_user"/>

                        <button name="action_quotation_send" string="Send by Email" type="object" states="draft" class="oe_highlight" groups="base.group_user"/>

                        <button name="action_quotation_send" string="Send by Email" type="object" states="sent,progress,manual" groups="base.group_user"/>

                        <button name="print_quotation" string="Print" type="object" states="draft" class="oe_highlight" groups="base.group_user"/>

                        <button name="print_quotation" string="Print" type="object" states="sent,progress,manual" groups="base.group_user"/>

                        <button name="action_button_confirm" states="draft" string="Confirm Sale" type="object" groups="base.group_user"/>

                        <button name="action_button_confirm" states="sent" string="Confirm Sale" class="oe_highlight" type="object" groups="base.group_user"/>

                        <button name="action_view_invoice" string="View Invoice" type="object" class="oe_highlight" attrs="{'invisible': [('invoice_exists', '=', False)]}" groups="base.group_user"/>

                        <button name="302" string="Create Invoice" type="action" states="manual" class="oe_highlight" groups="base.group_user"/>

                        <button name="copy_quotation" states="cancel" string="New Copy of Quotation" type="object"/>

                        <button name="cancel" states="draft,sent" string="Cancel Quotation" groups="base.group_user"/>

                        <button name="action_cancel" states="manual,progress" string="Cancel Order" type="object" groups="base.group_user"/>

                        <button name="invoice_cancel" states="invoice_except" string="Cancel Order" groups="base.group_user"/>

                        <field name="state" widget="statusbar" statusbar_visible="draft,sent,progress,done" statusbar_colors="{&quot;invoice_except&quot;:&quot;red&quot;,&quot;waiting_date&quot;:&quot;blue&quot;}"/>

                </header>

                <sheet>

                    <h1>

                        <label string="Quotation " attrs="{'invisible': [('state','not in',('draft','sent'))]}"/>

                        <label string="Sales Order " attrs="{'invisible': [('state','in',('draft','sent'))]}"/>

                        <field name="name" class="oe_inline" readonly="1"/>

                    </h1>

                    <group>

                        <group>

                            <field name="partner_id" on_change="onchange_partner_id(partner_id, context)" domain="[('customer','=',True)]" context="{'search_default_customer':1, 'show_address': 1}" options="{&quot;always_reload&quot;: True}"/>

                            <field name="partner_invoice_id" groups="sale.group_delivery_invoice_address" context="{'default_type':'invoice'}"/>

                            <field name="partner_shipping_id" on_change="onchange_delivery_id(company_id, partner_id, partner_shipping_id, fiscal_position)" groups="sale.group_delivery_invoice_address" context="{'default_type':'delivery'}"/>

                            <field name="project_id" context="{'partner_id':partner_invoice_id, 'manager_id': user_id, 'default_pricelist_id':pricelist_id, 'default_name':name, 'default_type': 'contract'}" groups="sale.group_analytic_accounting" domain="[('type','in',['view','normal','contract'])]"/>

                        </group>

                        <group>

                            <field name="date_order"/>

                            <field name="client_order_ref"/>

                            <field domain="[('type','=','sale')]" name="pricelist_id" groups="product.group_sale_pricelist" on_change="onchange_pricelist_id(pricelist_id,order_line)"/>

                            <field name="currency_id" invisible="1"/>

                        </group>

                    </group>

                    <notebook>

                        <page string="Order Lines">

                            <field name="order_line">

                                <form string="Sales Order Lines">

                                    <header groups="base.group_user">

                                        <button name="303" states="confirmed" string="Invoice" type="action" icon="terp-document-new"/>

                                        <field name="state" widget="statusbar" statusbar_visible="draft,confirmed,done" statusbar_colors="{&quot;exception&quot;:&quot;red&quot;,&quot;cancel&quot;:&quot;red&quot;}"/>

                                    </header>

                                    <group>

                                        <group>

                                            <field name="product_id" context="{'partner_id':parent.partner_id, 'quantity':product_uom_qty, 'pricelist':parent.pricelist_id, 'uom':product_uom, 'company_id': parent.company_id}" groups="base.group_user" on_change="product_id_change(parent.pricelist_id, product_id, product_uom_qty, False, product_uos_qty, False, name, parent.partner_id, False, True, parent.date_order, False, parent.fiscal_position, False, context)"/>

                                            <label for="product_uom_qty"/>

                                            <div>

                                                <field context="{'partner_id':parent.partner_id, 'quantity':product_uom_qty, 'pricelist':parent.pricelist_id, 'uom':product_uom, 'uom_qty_change':True, 'company_id': parent.company_id}" name="product_uom_qty" class="oe_inline" on_change="product_id_change(parent.pricelist_id,product_id,product_uom_qty,product_uom,product_uos_qty,product_uos,name,parent.partner_id, False, False, parent.date_order, False, parent.fiscal_position, True, context)"/>

                                                <field name="product_uom" groups="product.group_uom" class="oe_inline oe_no_button" context="{'company_id': parent.company_id}" on_change="onchange_product_uom(parent.pricelist_id,product_id,product_uom_qty,product_uom,product_uos_qty,product_uos,name,parent.partner_id, False, False, parent.date_order, parent.fiscal_position, context)"/>

                                            </div>

                                            <label for="product_uos_qty" groups="product.group_uos"/>

                                            <div groups="product.group_uos">

                                                <field name="product_uos_qty" class="oe_inline"/>

                                                <field name="product_uos" options="{&quot;no_open&quot;: True}" class="oe_inline"/>

                                            </div>

                                            <field name="price_unit"/>

                                            <label for="discount" groups="sale.group_discount_per_so_line"/>

                                            <div name="discount" groups="sale.group_discount_per_so_line">

                                                <field name="discount" class="oe_inline"/> %

                                            </div>

                                        </group>

                                        <group>

                                            <field name="tax_id" widget="many2many_tags" domain="[('parent_id','=',False),('type_tax_use','&lt;&gt;','purchase')]"/>

                                            <field name="th_weight"/>

                                            <!-- we should put a config wizard for these two fields -->

                                            <field name="address_allotment_id"/>

                                        </group>

                                    </group>

                                    <label for="name"/>

                                    <field name="name"/>

                                    <div groups="base.group_no_one">

                                        <label for="invoice_lines"/>

                                        <field name="invoice_lines"/>

                                    </div>

                                </form>

                                <tree string="Sales Order Lines" editable="bottom">

                                    <field name="sequence" widget="handle"/>

                                    <field name="state" invisible="1"/>

                                    <field name="th_weight" invisible="1"/>

                                    <field name="product_id" context="{'partner_id':parent.partner_id, 'quantity':product_uom_qty, 'pricelist':parent.pricelist_id, 'uom':product_uom, 'company_id': parent.company_id}" groups="base.group_user" on_change="product_id_change(parent.pricelist_id, product_id, product_uom_qty, False, product_uos_qty, False, name, parent.partner_id, False, True, parent.date_order, False, parent.fiscal_position, False, context)"/>

                                    <field name="name"/>

                                    <field name="product_uom_qty" context="{'partner_id':parent.partner_id, 'quantity':product_uom_qty, 'pricelist':parent.pricelist_id, 'uom':product_uom, 'company_id': parent.company_id}" on_change="product_id_change(parent.pricelist_id, product_id, product_uom_qty, product_uom, product_uos_qty, product_uos, name, parent.partner_id, False, False, parent.date_order, False, parent.fiscal_position, True, context)"/>

                                    <field name="product_uom" context="{'company_id': parent.company_id}" on_change="onchange_product_uom(parent.pricelist_id, product_id, product_uom_qty, product_uom, product_uos_qty, product_uos, name, parent.partner_id, False, False, parent.date_order, parent.fiscal_position, context)" groups="product.group_uom" options="{&quot;no_open&quot;: True}"/>

                                    <field name="product_uos_qty" groups="product.group_uos" invisible="1"/>

                                    <field name="product_uos" string="UoS" groups="product.group_uos" invisible="1"/>

                                    <field name="price_unit"/>

                                    <field name="tax_id" widget="many2many_tags" domain="[('parent_id','=',False),('type_tax_use','&lt;&gt;','purchase')]"/>

                                    <field name="discount" groups="sale.group_discount_per_so_line"/>

                                    <field name="price_subtotal"/>

                                </tree>

                            </field>

                            <group class="oe_subtotal_footer oe_right" colspan="2" name="sale_total">

                                <field name="amount_untaxed" widget="monetary" options="{'currency_field': 'currency_id'}"/>

                                <field name="amount_tax" widget="monetary" options="{'currency_field': 'currency_id'}"/>

                                <div class="oe_subtotal_footer_separator oe_inline">

                                    <label for="amount_total"/>

                                    <button name="button_dummy" states="draft,sent" string="(update)" type="object" class="oe_edit_only oe_link"/>

                                </div>

                                <field name="amount_total" nolabel="1" class="oe_subtotal_footer_separator" widget="monetary" options="{'currency_field': 'currency_id'}"/>

                            </group>

                            <div class="oe_clear"/>

                            <field name="note" class="oe_inline" placeholder="Terms and conditions..."/>

                        </page>

                        <page string="Other Information" groups="base.group_user">

                            <group>

                                <group name="sales_person" groups="base.group_user">

                                    <field name="user_id" context="{'default_groups_ref': ['base.group_user', 'base.group_partner_manager', 'account.group_account_invoice', 'base.group_sale_salesman_all_leads']}"/>

                                    <field name="section_id" options="{'no_create': True}" groups="base.group_multi_salesteams"/>

                                    <field groups="base.group_no_one" name="origin"/>

                                </group>

                                <group name="sale_pay">

                                    <field name="payment_term" options="{'no_create': True}"/>

                                    <field name="fiscal_position" options="{'no_create': True}" on_change="onchange_fiscal_position(fiscal_position, order_line, context)"/>

                                    <field name="company_id" widget="selection" groups="base.group_multi_company"/>

                                </group>

                                <group>

                                    <field name="invoiced"/>

                                    <field name="invoice_exists" invisible="1"/>

                                </group>

                            </group>

                        </page>

                    </notebook>

                </sheet>

                <div class="oe_chatter">

                    <field name="message_follower_ids" widget="mail_followers" groups="base.group_user"/>

                    <field name="message_ids" widget="mail_thread"/>

                </div>

Hi!

Please check your currency settings. Perhaps, in the field 'symbol' it is indicated twice?

If no, could you plase active the debug mode and send the final xml of this form?

Hi, Any solution for the same ?

I am getting same issue on my server. If i am restoring server database on my local machine every thing is working fine but not on server.