I was wondering *if* the paint had metal in it, if it were sitting in direct sun, especially darker paints, heats the paint up enough and allows the flakes to be attracted towards the magnets.
the paint softens in the high heat, and the textured rubber backing behind the magnet embeds into the finish, leaving a little bumpy area where the magnet was attached.
yes, all paints get soft in hot sun, brittle is cold weather. paint is meant to me on top of something expanding and contracting as needed. when you sandwich or put something on top of it. everything from sun fade,crushing,denting,scratching,scuffing, etc, etc, etc. can and will happen.
cars, bikes, soft materials, hard materials, its all the same thing.
just trying to help you guys protect your paint.
also tank bags on a hot day while covering the gas cap will capture, keep the fumes,even alter the rubber or plastic on the tank bags and also react to the paint.
gas fumes,vapors are VOC= volatile organic compounds.