Sounds like a bad driver, what happens when they over heat is they just stop following commands until they are cool enough to work again. Overheat protection. The drivers are sensitive to all kinds of things. If you unplug a steppers while there is any power going to it chances are the driver is dead. $5 get a new one before it wrecks and expensive stepper or the ramps.
Unfortunately I am sold out. DHL might be dropping some off today, but not 100% sure about that.