Thank you for your post.
There were some issues with commands sporadically not working on Mac OS X. Another issue where the Edit Menu Commands would temporarily stop working after Printing. I would first recommend updating to FileMaker Pro 14.0.4 and see if the issue persists. You can find the download for FileMaker Pro 14.0.4 updater here: Get A FileMaker Download or Database Update.
I hope this information is of use, let me know if your issue persists.
Thanks. I will try. Now that you mention it, this did seem to occur after printing.
On a similar setup, I have sometimes found Copy and Paste commands don't work from keyboard shortcuts. My experience generally is that it is command+C (copy) that doesn't work rather than command+V (paste). It's possible that you think it is Paste that is not working, but in fact it only appears this way because there is nothing on the clipboard to paste, and this is because Copy did not work. I have proven this to be so by using Copy direct from the menu, then using command+V to paste. Try it yourself.