Just realized my DA sander was eating my filler jobs because of a $4 pad

Last month I was blocking out a quarter panel on a silver Camry and the sand scratches kept showing up under the sealer no matter how many passes I made. I pulled the pad off my DA and the backing plate had a chunk missing, so it was orbiting off center and digging in on one edge. I swapped on a fresh 6 inch pad I had in the drawer, reblocked the panel with 180 then 320, and the scratches quit showing up completely. What got me was that the pad looked fine from the top, only the back side showed the tear. I've started checking the backing plate every time I change paper now, which sounds dumb but it saved me a repaint. Any of you caught a bad pad by feel before it ruined a job?