Casio VF-3000 (similar to Hitachi/RCA VHS camcorder) tape path issue

[CPQ5360]

Hi all - I recently procured a circa 1988 Casio VF-3000, a very rare portable TV/VCR based on a Hitachi/RCA VHS camcorder mechanism.

The mechanism has a minor issue - while playing a tape, slack forms on one side of the tape at the pinch roller, which eventually folds over and makes a long diagonal crease in the tape. It only happens sometimes, but when it does, it does it repeatedly, every few seconds.

The pinch roller is a little on the smooth/hard side, but not bad. I cleaned it with alcohol and roughened it up a little with an emery board, but that hasn't helped.

I have a video of it here:

https://www.youtube.com/watch?v=L4LZXsoJgg8

Any ideas? It almost seems like a guide is misaligned, making the tape move slightly diagonally, but I really don't know. Any help is appreciated.