Update: I took the faceplate off again to investigate. Every function works well if I hold the tape tension bar in place to make the motors activate. Fast rewind working great. I put a tape on it, the rewind struggles, though it does a little better than with the faceplate on. A little.
Can't...
I just put new belts in a Sony TC-366 and have found that when the faceplate is put back on, rewind is incredibly sluggish. The deck struggles to rewind and I have to hold the knob in RW to even get it to do that. Playback and Forward are fine. Prior to changing the belts, the issue was present...