I’ve had this happen when the bit hits a clamp and binds. Turn the machine off (as in turn the switch off on the tower). Wait at least one full minute (I always wait a couple of minutes), then turn it back on. Basically a ‘hard boot’. That has always worked for me.
I should also have mentioned, that if that does not work, they (Inventables Tech Support) have another way of fixing it. Not sure what that is because turning it off and on has worked for me the few times that it happened to me.