I've added a second Purchase Orders view in my left-side menu. The first Purchase Orders view is the default one bundled in Odoo 8. The second Purchase Orders view should have different columns. This is the xml of the second view:

<record id="view_purchase_order_with_core_product" model="ir.ui.view">
    <field name="name">my.custom.PO.view</field>
    <field name="model">purchase.order</field>
    <field name="type">tree</field>
    <field name="priority">1</field>
    <field name="arch" type="xml">
        <tree>
            <field name="product_id"/>
            <field name="message_unread"/>
        </tree>
    </field>
</record>

<record id="act_purchase_order_with_core_product" model="ir.actions.act_window">
    <field name="name">Second PO view</field>
    <field name="type">ir.actions.act_window</field>
    <field name="res_model">purchase.order</field>
    <field name="view_mode">tree,form</field>
    <field name="context">{}</field>
    <field name="domain">[('has_core_articles', '=', True)]</field>
    <field name="view_id" ref="view_purchase_order_with_core_product"/>
</record>

<menuitem id="menu_purchase_order_with_core_product" name="Second PO view"
          parent="purchase.menu_procurement_management"
          action="act_purchase_order_with_core_product" sequence="14"/>

The purpose of that second view is to display only orders which contains certain articles, display differents columns than the original view.

I've managed to do the filter using the domain field (I didn't want to use the search filter for that).

My problem is that when I modify the columns of my second views, the original view (the first view) is also modified and display the extra columns.

What am I doing wrong ?

EDIT: I've removed the priority field but I still have the same error after upgrading my module