I think i know what he means....i just fitted some new pads, and they were like 1mm too big to fit inside the calliper, so we had to file them down a tiny bit so they would fit. But these were performance pads not from factory, so i wouldn't have thought it would be that??
Also in the box, there were some black stickers to go on the outside of the pads. As I’m a noob with cars i thought what the hell is that for? I was told, it will stop them from squeaking. Not sure if this is true??? So maybe they forgot to put a sticky pad on one of the pads in the factory? I am not an expert just thought I’d mention it.
I'd go with the possible stone or something tho, as it's so new....