Cheese slopes, the red ones in my 2011 Star Wars Advent Calendar were pretty much garbage out of the box, had them all replaced as even those that didn't fall in two almost immediately looked like they were starting to crack, the replacements didn't, I've seen other ones crack though offhand I only see 1/2 of a white one the vacuum cleaner ate.
A local used store where some of the bulk used gets sorted put a pile of sand green in the dig bin, but it had been sorted, the only parts that went in were cracked 1x bricks, and a lot of them, but again, possibly all came out of one batch, having seen soda made/packaged, same flavor running on 4 production lines, 2 sizes of bottles, 2-3 different case sizes for cans at the same time, obviously if doing plastic (also a liquid in the process), you may be running more than one size of mold with the same batch of goo.
I've had other pieces crack, probably some plates, but then some of them were probably abused some as well.