After upgrading to FMP14 we've run into an intermittent bug with drop-down lists. After opening the database and using it for 15-30 minutes the drop-down lists on some fields quit working. You can click on the arrow to show the list, but FMP doesn't draw the list.
If the user changes layouts and returns to the layout, the list will draw again for a little while, then quits again. If the user starts to type something that matches any list entry, it will auto complete. FMP will then start drawing the list again for a little while. Closing FMP and re-opening the database always fixes the problem for 15-30 minutes.