Okay I've removed the springs from the cash box. The bill is still getting stuck right between the exit of the head and the entrance to the transport. I listened to the gears to see if they sound any different, but it seems they're the same unfortunately.
Today I'm gonna see if I can see anything that's blocking it from going. I noticed when the bill is in this position and I manually turn the gears by hand it doesn't go anywhere.
Edit: so the bill gets folded up multiple times in the mechanism. I took the top cover off the transit and watched it start up. I noticed the belt in the picture isn't moving much at all. It kinda turns a bit very weakly during the startup. The roller on the other hand spins freely.
Think it might be related to the belt? (I've noticed the bill gets as far as a little past the roller)
Edit again: the roller in the picture doesn't actually move when the bill is stuck in it. It tries to move which is the sound in the video of the gears turning but it's not actually turning.