Aha. OK, problem seems to be solved.

I went through the process of deleting the duplicated button, saving the file to disk, then adding it back; being very careful not to overlap with other buttons in anyway. Downloaded to the remote and relearned the function and it works just fine! This was apparently the problem I'd been having with my Sony TV "vid1, vid2" etc input source buttons not working.

Thank the consumer electronic gods for this website. Manufacturers' support being what it is I was almost ready to return the remote...

(I hope Universal Remotes heard that... ;-)