I've been facing a really bizarre problem on my 15" 2011 MBP running El Capitan over the past couple days.

Sometimes - possibly more often, or exclusively, under high load - some apps will suddenly no longer react to key presses entered in text areas and input fields, for example:

  • in the URL bar in Safari
  • in all input fields when writing an E-Mail in Mail.App
  • in Spotlight's search bar

However, hotkeys (e.g. Cmd+Q to quit the app) still work!

Also, when I switch to a different app, keyboard input will work there as expected. Then when I go back to the app with the problem, it'll be broken again.

This never happens in all apps at once - right now, for example, Spotlight doesn't accept any input, but the browser with which I'm writing this question works (obviously).

This is not a hardware problem: it occurs on both my Bluetooth Apple keyboard, and the MBP's built-in keyboard.

Quitting the application in question will help for a couple of minutes, then it'll happen again. Restarting the machine doesn't help.

I'm not seeing any weird processes or anything in the process list.

What could be causing this?

  • What version of El Capitan? Jan 10, 2017 at 21:09
  • @Kaizerwolf I think it was .6. I since decided to try and fix this by updating to Sierra. Big mistake.
    – Pekka
    Jan 11, 2017 at 22:17


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