I had the same experience with cheapo Performance brand SPD pedals. The first set literally set fell apart as I was riding one day and would no longer hold the cleat. With the second set (at least it was a free replacement) my foot would occasionally come out without warning. Obviously, this is very dangerous when climbing out of the saddle or going over rough patches. I just purchased Shimano Deore XT pedals on sale at Performance. What a difference quality makes. I'll never skimp on pedals again.