The larger belt on the side where motor is might still have ended up crooked. Either way great job on this. Ticking in the background made it sound like you're working on a time bomb :). Oh and it'd probably be a good idea to calibrate tape speed after fitting new belts.
Now you come to mention it, and looking at the video in detail, I think you may be right - there was still a twist in that belt! I don't have the machine any more as I didn't really have any use for it and it would have just sat on a shelf doing nothing, so passed it on to someone else who can get some enjoyment from it. Unfortunately, as a hobbyist on a tight budget, I don't possess the necessary equipment to calibrate the tape speed, but it sounded about right to me. (The time bomb is a future project.)
@@timf-tinkering The only real cost in tape speed calibration is obtaining a decent test tape. Other than that you need a screwdriver and either a PC (WowFlutterMeter free software) or a smartphone (I use Spectroid).