Could it be the same board (with the mystery traces) is also used for
other model vcr's where the traces are actually used. Or could it be a
kind of ground trace where the intended purpose is not so apparent.

Have you considered the motor driver(drum) maybe partially failed in
that it is not delivering enough current, and in turn drum torque.

Skype_man's suggestion makes sense as well in that the power to the
drum must be clean. Sounds like it will take a bit more
checking and probing. I'll bet the driver passes the diode test since
it at least partially works. It's an interesting problem, keep us
informed of your progress. I had a similar problem years ago. Hard to
remember exactly how I fixed it.

Dennis H.