One of the processes keeps sending a keystroke repeatedly in the background, how to identify the culprit?

Question

My system is a MacBook Pro late 2013 running macOS Sierra 10.12.6.

Symptoms:

Occasionally after the laptop wakes from sleep, the system would behave as if someone is repeatedly pressing a certain key on the keyboard.
If I click anything (Apple icon, File, Edit...etc) on the menu bar, the item whose name starts with A will be highlighted repeatedly, B if nothing starts with A, and so on. (Therefore, I assume the keystroke being sent is a number.)
If I press cmd+tab attempting to switch between apps, the focus will automatically scroll all the way to the right-most item.
This doesn't affect all apps. I am able to use Chrome as if there's nothing wrong.

My question:

Apparently one or more of the processes running on my system is doing this. To find out which process / app is sending the keystroke, I am looking for a way or a tool to monitor who is sending keystroke. Therefore next time this happens I can use this to determine the culprit.

Thanks!

Is it possible your keyboard is malfunctioning, or there's another keyboard connected (maybe a Bluetooth wireless keyboard)? — Gordon Davisson, Commented Apr 15, 2019 at 6:49
I don't have any Bluetooth keyboard and the only Bluetooth devices I use are headphones, which are usually not turned on when this happens. It doesn't feel like a hardware malfunction because it only happens, occasionally, after waking up from sleep. If it was a keyboard issue, I think I would notice it more frequently and not only after sleep. — Vic Jang, Commented Apr 15, 2019 at 18:34

Vic Jang · Accepted Answer · 2019-05-31 11:34:01Z

0

It turned out that the culprit was Karabiner-elements, and the issue has been resolved in the latest update.

answered May 31, 2019 at 11:34

Vic Jang

7666 silver badges9 bronze badges

Add a comment |

1 Answer 1