I use Option-Enter A LOT. My main uses are to put a new line into a message in Messages, and to open a url in a new tab in Google Chrome, I know I can hit Command-T, but I often want to modify the url slightly and open in a new tab in one fell swoop.
This used to work fine all the time, now it will work for a while and then stop until the next reboot. I have looked at System Preferences->Keyboard->Shortcuts and there's nothing defined for Option-Enter.
If there is a likely culprit, please let me know. Otherwise, if you could explain how to determine which App or process is affecting this.
Running El Capitan 10.11.3