Sony SVO-5800P error 02-674 (sticking motor)
 

I've recently bought a Sony SVO5800P SVHS player which has played tapes perfectly for about 20 hours.
It has now developed an issue where it will stop with error 02-674 or 02-676 after about 3 mins of playing. It will then bring the error up more and more frequently.
I've taken the top and bottom off. On the top you can see the tape occasionally gaining slack and when it gains too much, the error kicks in.
You can also hear a quiet clicking on every rotation of the cassette spindle. (I should mention here that I have tried multiple tapes!)
On the bottom you can see one motor occasionally sticking and when it sticks for too long, the error kicks in. You can also feel friction and the point where it sticks. However when the tape is out, the motor spins completely freely.
Both brakes seem to be fully released, so not that.
Any suggestions to what may be causing the sticking welcome. Here's a quick video of the bottom of machine when the error happens (see the bottom motor stick after 3/4 turn, after tape is inserted and pressed play):
https://youtu.be/voaRHCK4WZU
Bonus info: when I flipped the machine back up, a small torsion spring had fallen out. Machine works (apart from error issue) and can't see anywhere where it should go. Not convinced it is related though.