I have a Ryobi PSA that I never have trouble with. I just picked a Makita and replaced the PSA backing pad with a new one. The new one will not hold discs. I get about 5 minutes of sanding and then the disc is off across the room. The Ryobi seems to have a much firmer backing pad than the Makita and I wonder if there is too much flex in the Makita backing pad which might be causing failure in the glue. The Makita pad also has little bumps on it while the Ryobi is completely flat. The Makita is running at 12000 rpm while the Ryobi runs at 11000. With the problem I am having I am thinking of sanding off the bumps on the Makita and maybe running it through a rheostat to slow it down a bit. Another thing I might try is to find a thin rigid backing pad and gluing it to the makita pad to provide a firmer surface.