Let me guess, a kid left a Crayon in their pocket, which made it through the washer and into the dryer? I've actually had to do this because a Crayon got stuck on the tub seal (the back one, of course) and would leave stains on the clothes. Not just any crayon, mind you, but TWO crayons, red and green. The missus couldn't find them, so she made me take the dryer apart. I was NOT a happy camper when I found out what had happened, because the dryer was only about 3 months old, and had ruined several pairs of very expensive FR jeans and shirts. Any grease or paraffin on FR clothing makes it no longer FR. The kids went into hiding for a while. Pretty sure the missus put them in WitSec until I calmed down. It's probably a good thing I didn't yet have a tractor with a front-end loader.
That actually looks like a front load washer, though.