Mouse Keys randomly enabled. How can I prevent this?
Default trigger switch for Mouse Keys is to hit  Opt ⌥   5 times.

You will usually hear the little 'zipper' noise it makes as it switches.

Occasionally, you can trigger it accidentally with seemingly unrelated presses of  Opt ⌥ . To reverse it, just tap it 5 times again.

To disable it entirely, System Prefs > Accessibility > Mouse &amp; Trackpad > Options... &amp; uncheck