I have a 2nd-gen 13" MacBook Pro; basically the last version without a retina screen.
My "B" key no longer functions as a "B" key; instead it launches iTunes. Occasionally, if I hit a different key immediately beforehand, I can get it to actually insert a "b" into whatever I'm typing, but it usually takes a few tries. "esc" appears to have similar behaviour.
This only began happening recently, within the past couple of days. It may have coincided with a recent OS upgrade to High Sierra, but I haven't been paying too close attention. I don't believe I made any other major system changes.
- This happens both on the built-in laptop keyboard and a USB keyboard.
- I can type "b" as part of my password in the login screen before I am logged in.
- I have quit every visibly running app and the problem persists.
- I have turned it off and on again.
- I have reinstalled the OS from recovery mode.
- I do not somehow mistakenly have the "b" key set to anything in the keyboard shortcuts settings.
- My keyboard is set to US in "Input Sources".
- Here is a video showing the phenomenon.
What else can be done to diagnose this issue? What log files should I be looking at? What configuration options am I missing? Is there anything I can do, short of backing everything up, wiping the hard disk, and starting over?