RCA VFT650 won't play; pinch roller won't engage

[CPQ5360]

I recently acquired an RCA VFT650, a top-loading VHS machine from 1981 based on the Panasonic PV-1770. I replaced the belts, cleaned the idler tires, and cleaned the mode switch, and I currently have it working as far as being able to rewind, fast-forward, and load a tape.

There's a couple of weird issues that have me stopped up right now. First is that the pinch roller doesn't engage when the tape is loaded. When I try to move the arm by hand, it is very stiff. The second issue is that when the tape is loaded, it plays for a split second and then immediately aborts and unloads the tape. I don't know if this is related to the pinch roller issue or not.

I'm guessing the pinch roller arm should be able to move freely, and that there must be dried grease or something gumming it up? Should I try using WD-40 or something to break up the grease? Or might something else be wrong? Thanks for any ideas!