I modified the name of an existing menuitem (Customers in Sales). I did it this way:

<record model="ir.ui.menu" id="base.menu_partner_form">
     <field name="name">Contacts</field>
</record>

It's working, but to see the changes, I have to load the translation and synchronize the terms.

The problem is when I try to modify the name of an ir.actions.act_window. I applied the same method but it only worked the first time. Then, I had to load again the translation and synchronize the terms due to other reasons, and both menuitem and action removed my changes. When I repeated again the process, only the menuitem loaded my changes.

This is the code of the action:

<record id="base.action_partner_form" model="ir.actions.act_window">
     <field name="name">Contacts</field>
</record>

Am I doing it well? Why is this happening?