Bug: Assignment rule

Hi, It seems there is bug in assignment rule

These rules work fine:
Purchase order → Assign condition: status == “To Receive and Bill”
Material request → Assign condition: material_request_type == “Purchase” and status == “Pending”

These rules does not work:
Purchase order → Unassign condition: status != “To Receive and Bill”
Material request → Unassign condition: status != “Pending”

It seems assignment rules cannot work at all with some doctypes. Example these rules does not result in any Todo created:
Purchase receipt → Assign condition: status == “To Bill”

Would appreciate you help to test on your system.
Is it user error on my side, or is it a bug?
Im on ERPnxt v12.5.2

Many thanks

Have you solved the issue? I have trouble with the unassign rule as well.