Holding down a key on the keyboard does not cause it to repeat correctly. The key will repeat, but only after 2 seconds or so. In some cases it doesn't repeat at all. There are a few suggestions floating around in forums but none seem to correct the problem.
Settings in preferences are ignored:
Interestingly, key repeat does seem to work in Terminal, but that's the exception. It's broken in Notes, Mail, TextEdit, etc.
Any ideas?
Best Answer
This bug was fixed by Apple in macOS 10.12.1, released a few hours after I wrote the above ...