stuck key at login
My mac bluetooth keyboard frequently acts like a key is stuck at the login screen. It only happens at the login screen and there is no physically stuck keys. I have to turn off then on the keyboard to fix it. sometimes I have to do more than once. Any ideas on how to fix it?
iMac (Retina 5K, 27-inch, Late 2014), OS X El Capitan (10.11.1)