I've had my caliper lock up twice in the last week when I've used the E-brake. I have to drive for about 2 miles, get it really hot, and then turn off my car for about 1 minute. then it will unlock. WTF is going on? It isn't cold enough to freeze, and I replaced the rear calipers last spring. I don't want to warp or crack my rotors, so what should I do?