If you go to coil Y48.4 in your ladder and scroll up you will come across a function block SUB9 COM. What this function block does is set all the coils to OFF between the SUB9 and SUB29 COME (COM END). If you scroll down you will see SUB29. Your clamping circuit is between these two SUBs. If SUB9 is on the logic works as if you didn't use COM in the first place. You will have to verify that COM is on when you are trying to clamp.