Ah, end users and basic printer maintenance...
I've got many, many stories of users messing up printers beyond repair while trying to solve basic tasks, here's some highlights:
1. A brave attempt at swapping out a toner cartridge. Unfortunately the user didn't realise a locking tab was in place, which also closed the opening in the cartridge. Their solution was to simply apply more force. Aftermath? The room was coated top to bottom in black carcinogenic dust! It genuinely looked like an explosion had taken place, the entire printer was coated, and a streak ran up the wall across the ceiling over to the other side! Bonus points for the brave soul who wanted to clean this up using a wet mop, at least they tried. I ended up printing a biohazard sticker (on a different printer) and sticking it on the door, and calling in a professional cleaner. I really wish i could've seen the perpetrator, this stuff is probably worse than the ink bombs they use for money.
2. Paper jam in a small simplex mono printer (i mention this because it's not some large MFP with a bunch of rolls and pulleys). They managed to solve the paper jam using their tool of choice: a knife! Unfortunately they also stabbed the drum to death. Of course none of this was mentioned in the service request, the printer just stopped working. We were shocked the first time, ended up replacing the printer (drum replacements weren't economically viable for those small printers). End of story? Nope! less than a week later the exact same story! The client followed our recommendation, and they implemented a new policy for that location, where only a few select users were "trained" at refilling paper, and any other task had to be performed by service techs...
3. Printer in a primary school, for some reason there weren't any rooms available that children couldn't reach. They called because of a really bad paper jam and a bunch of error codes. I have no clue how, but a child had managed to jam a colored pencil waaay into the innards of the printer. I was genuinely impressed! (I'm saying it was a child, but i have no way to be sure of that. It's a bit of a coping mechanism to assume it's a child, but realistically it could've been another improvised tool to "solve" a paper jam.)