One of my worst memories in aviation was back in 2007 when a passenger flushed a can of Coke down the toilet and it wound up blocking the line on a 767. The engineer had to rip up half the floorboards to inspect where the blockage was and then very carefully cut into the line to remove the can and manually remove other blockages. All this with 200+ passengers looking on and agitating to board at the gate. Took us over 3 hours and my word, we stank at the end of it.
More recently, an older 320 had a problem with the locking mechanism on the suction tube and began leaking around the edges. The poor lav truck driver had to literally hold the tube in place while various brown substances dripped down the edges and over his hands (heavy duty gloves thankfully) until the tank had been drained. It was either that or release his grip to hit the shutoff in which case the tube could have detached and splattered his face. He chose the lesser of the two evils.
Lav truck duty always comes up with some crappy stories! 🙂