I'm struggling with this mech

The issues (under normal tension):
1) kinda hard to insert the tape (but if i force a little it goes in 1 time out of 3)
2) The tower gear seems stuck -> the pinch roller won't go down whatsoever

What i did so far:
-remove/clean old gunky grease (and there was a lot on gears) / general cleaning / regrease
- partial cleaning of the mode switch encoder (external contacts only->oxydized) couldn't find a way to completely disassemble, that's some type i'm not familiar with and i don't want to break it
- the loading motor works just fine (tested with a 12v psu, it completes the loading cycle just fine)
- Main Belt seems about right (i didn't disassemble, just checked the tension)
- Capstan / Drum seem to work right (turn)

I get the feeling something's not right with a sensor / supply or take up reel

I'd love to get my hands on the service manual (couldn't find one for free)

Ideas welcome

-- merged --

Fixed, crack on the coupling on the motor , i've superglued all that
And also entirely cleaned the mode switch (found a way to disassemble it with a little knife on top of the shaft)

Same loading motor coupler and crack that the AG1980 gets I see.

These couplers will probably fail again after just super glueing. If the coupler is not available new and there is space available on the coupler, I would carefully wind many turns of cotton thread around the circumference of the coupler for added strength and then apply super glue (not gel) to the cotton winds. Best to wind the cotton tightly to help close the crack and prevent it reopening there or in another place. All done of course while the coupler is off the motor shaft.