I removed 2 springs from the 2 film hold down clamps.
The outer left spring and the outer right spring leaving the 2 inner springs.
This still will put pressure to hold the film down closest to the scan area.
As such there was far less tension on the film and it moved much easier !
Ran the same...
There was no "coil spring" in my unit (where was this on yours) and the only slip mechanism is the drive belt sipping over the cogs on the 2 gears.
I have not had a chance to play with my unit again but I'm thinking my motor speed mod is the way to go.
This would be putting the correct size...
New here so excuse me if my post is different for other versions (I have an A version per 0Dan0's list).
Popped the back off and removed the motor assy.
Removed the snap ring and the second large gear.
Removed the 4 screws and black retaining cap (I guess you could call it ) and the 3 washers...