The default shortcuts (e.g. Cmd-N) switch themselves off for no reason

Issue report by glenmac451

Product

FileMaker Pro

Version

13

Operating system version

OSX 10.10

Description of the issue

I will use a database for a while using the built in shortcuts like Cmd-N, Cmd-J. Suddenly they will no longer work.
I can fund the Command in the Menu bar, and it will work, but the note of the short cut has also vanished.
These are long established databases I am using and have not given problems before.
I have not changed anything in the background.
closing down FM and reopening brings back the defaults, but they disappear again, in due course. Highly irritating
Comments would be appreciated

Steps to reproduce the problem

Don't know