After the last beta update to macOS 10.14.6 I found myself confronted with a misbehaving trackpad. A two finger tap was supposed to be a "secondary click" (a.k.a. Control+click) but instead the windows on my screen were acting strangely and moving all over the place. The only way I could open context menus, etc. was to hold down the control key and tap on the trackpad with my finger. This was happening with both built-in trackpad and the wireless Magic Trackpad on my MacBook Pro.

Suspecting a Preference Setting had been changed during the update, I checked all the settings in System Preferences > Trackpad and they were correct. I searched for the trackpad property list (I still haven't found it). I rebooted — several times in hopes the results would change I guess. I boot from a clone — same results. I searched the public beta forums for someone reporting similar problems — none found.

By this time I had figured out the action I was seeing was Mission Control (a function I never use — but I may well start using after seeing what it does). In desperation and/or frustration I started using the wired Apple mouse I had plugged in a few days back just so I could get a working secondary click function. I right clicked on it and — MISSION CONTROL! 🤬 Back to System Preferences but this time the Mouse pane, where the right button was set to — you guessed it — Mission Control. Surely the Mouse setting could not override the trackpad setting. Maybe not, but it does! 😡

Changing the setting in System Preferences > Mouse or unplugging the Mouse, thereby preventing the Mouse Preference Pane and drivers from loading, immediately restored the trackpad to its proper functionality and I can once again use a two finger tap to get Context Menus and other functions. 👏 👌 👍 🎺

I had forgotten a troubleshooting lesson learned long ago that getting over-focused on the effect can too easily distract you from discerning the cause.

PS: This has been reported to Apple through the beta tester Feedback system.


If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein