When there are required fields that are not completed you should get a popup, not just a discreet error message

If you in D365 set up required fields for Time registrations and fault fields this sort of works. However initially everything seems ok, a user has to actually notice the small error number in the lower left side and read the message.

Better solution:

This should be a stop fault when trying to change status, you should simply not be allowed to change state to completed before filling out whatever is required.