Just a thought. Over all my years with these printers I've found that simply turning the printer off and then restarting doesn't always do what you might think it should do. I have found that if I need to power off the printer to perhaps fix an issue, I also need to pull the plug. In that case I would let the printer sit for a few minutes before plugging in and then a restart. Not sure why that works, and certainly not saying it might work for your printer, but it can't hurt to try. That is indeed a rather peculiar issue to track down.
Wishing you good luck, hopefully soon. 😀👍👍👍
EDIT: One more possibility. Check to see if the Paper Size Check is ON. If not, turn it ON. I have no idea how it could have been be turned OFF, unless by accident, but a look will confirm that.