Update button; "file doesn't exist" problem

I have, since Pano 6, in the single-record view of certain databases a field UPDATE and a push button next to it to trigger the update with the procedure:

field UPDATE
cell today()

I installed the same in one Pano X database where it works flawlessly. I tried to transfer (copy) it to another Pano X database and checked it had the same settings for the button and the UPDATE field but it doesn’t work. I wonder what am I doing wrong?

By the way, I am getting again frequently the message: “file can not be saved because it doesn’t exist”. Of course, autosave doesn’t work either for the same reason.
This usually happens after changes made in the Graphics mode. Whatever triggers this nastyness when it starts it only allows one (1) change in Graphics mode. This can be saved. As soon as I make 2 or more changes the ominous message comes up and I must force-quit. The changes are lost, of course.
This behaviour seems to disappear if I duplicate the database and start working with the duplicate.
Any known cure?

Just use: UPDATE = today()

Thanks, James! Simple, elegant and it works.