I managed to run my hot end into a binder clip a while back, and thereafter began having unusually high temperature spikes as shown in the interface.
The thermistor seemed to be reading the temperature accurately, but every so often it would spike high, ~250--270 degrees C or so, though the desired temperature was 200 (printing in PLA).
I've been reprinting the same file for a while now, and hadn't done anything else to change the machine.
Does it seem reasonable that something could have cracked in the hot end after the impact (external inspection didn't show any damage), creating a thermal break which would intermittently be bridged when things reached a certain temperature? If so, how would one test / check for that?
Anyway, to make a long story short, I experimented until I destroyed the hot end (guess it'll go in the box w/ the J-head I destroyed through willful stupidity and ignorance), so need to get a new one --- hopefully 3rd time's the charm.