Hey opponaughts I am hoping someone could shed some light on a wierd brake issue that has crept up this past week. I daily an 05 Scion TC with about 150k on the clock. Occasionally when lightly applying the brakes at low speed it seems as if the left rear caliper locks up and I get a loud grinding sound. It does not happen every time and I can not get it to happen on command either. Braking from speed is fine, no noise at all, peddle feel is normal, etc.

Any ideas?