2 different custom-Modules.

the first adds some fields to Sales-Order with the following XML:

<record model="ir.ui.view" id="sale_order_extended_form_view">
<field name="name">sale.extended_sale_order</field>
<field name="model">sale.order</field>
<field name="inherit_id" ref="sale.view_order_form" />
<field name="arch" type="xml">
<xpath expr="//field[@name='validity_date']" position="after">
<field name="order_type" class="oe_inline" required="True" />
<field name="factura_type_id" class="oe_inline" domain="[('order_type_ids','in',order_type)]"/>
<field name="factura_int" class="oe_inline" />
         <field name="valuta_date" widget="date" class="oe_inline" />
</xpath>.........

---

 now a new custom module should add one more field after the field order_type

we tried the following XML without success:

<record model="ir.ui.view" id="sale_order_extended_form_view_kassa_extend">

<field name="name">x_dummymodule2.extended_sale_order</field>
<field name="model">sale.order</field>
<field name="inherit_id" ref="x_dummymodule1.sale_order_extended_form_view" />
<field name="arch" type="xml">
<xpath expr="//field[@name='order_type']" position="after">
<field name="tmp_id" class="oe_inline"/>
</xpath>
</field>
</record>

while updating the new Module we get constraint-validation errors that tell about fields defined in the first custom module.

how can we inherit from the View of the first-custom module?