I've rebelted the bottom deck with fresh new belts of the correct size (FM9.6 + SBS8.9), cleaned all the gears in both belt's paths, and everything works. However, rewind performance is not good. With a 90 minute tape, it will work until it's within 10% at the start of the tape, then it doesn't seem to have enough torque to keep it running.
I've tried varying belt sizes/tensions, removing the counter belt for a little less resistance, but nothing really makes it work well. Even swapped out the motor with a beefier one, tried different tapes (it varies a little amongst them); no dice.
Does anyone have a C100/clone that does NOT have this issue? Is it just a weakness of this box/deck?