Thanks for your report @greatelec. This is being tracked by the Arduino IDE developers here:
In my experience, there are two variants of this issue:
transitory
This is caused by opening the menu while the IDE is still scanning the examples, such as occurs when you have just changed the board selection. This clears up if you wait some seconds and then open the menu again.
persistent
This variant persists no matter how long you wait. You must take action such as restarting the IDE in order to restore the correct functionality.
Even though I encounter it regularly, I haven't figured out exactly what the conditions are to trigger the "persistent" version. If anyone can figure out how to reliably reproduce it, please let me know.
