I\'m using Odoo 8 and I have a problem with compute field with type is Many2One.
Here, I declared department_id:
The store=True works.
It may be that you added the computation to the field after it was created on the database. In this case the initial computation is not triggered.
A work around is to drop the column from the table and then upgrade your module. When the field is recreated the initial values should be computed.