I've had this problem with my old LC pads that are used on the PC, though this is after sevral uses, the backing starts to come away... I suspect (though am not 100% sure) using them on the PC at speed 6 may be a part cause (heat generation), and I know
Meguiars dont recommend using their pads at over speed 5 on the PC for this very reason.
My
Meguiars pads on the rotary have been spot on though, including the cutting pads I use for OP knock back at above 2000rpm.