this is fun to read.
as i am only into black and white 35mm there is not too much.
the worst thing was: I loaded two rolls of film on two reels and put them in the drum. light on. everything worked out fine. except: there was an opened 125PX and a trix pushed to 2000 beside the loaded tank.
oh well. Of course I didn't know which one I had loaded first. Light out. one reel in a single drum each. Then I guessed and developed one. Turned out I developed the trix way too short. At least I knew for sure the 125PX was in the other drum.
Lost one film. Never happened again, till now. nobody ever did this?