First time this has happened. I'm stumped, and all my buddies who paint a lot more than me are also stumped.
Plastic magnetic tiles. Washed, scuffed with sandpaper. Spray primer that I've always used, acrylic paints. Wash, then let dry for days. Hit it with matte coat spray and it immediately does this. Not all tiles, just random, and the paint just wiped off. Once dried, seems solid, but cracked. I'm super angry for ruining this stuff, but also want to know what happened.