When switching between secondary profiles (switching to secondary profile to another, usually logged in for less than 10 seconds, and then switching back to the main secondary profile, using the 'select user' panel in the notification center, repeat 1-3 times), the lockscreen doesn't register any touches at all and I have to force restart.
In this state, the lock button sometimes work, sometimes doesn't; double clicking the lock button opens up camera before, but not now; volume buttons still work.
Been experiencing this about once or twice weekly for the past few weeks.