This is the right side one which sticks through the panel.
I always wish I had been trained by someone like an old Teac engineer (Skywave etc) As you can learn a lot from the older guys and they can put you straight "don't do this or that etc"
Sadly I have to bumble along, I am writing a longer description as maybe it will help someone or someone can correct me.
I am just doing a semi restoration on an unloved A-4010S, mine looks very difficult to everyone else's as I don't have so many leads or a PCB externally in the tape transport section.
Anyway this arm was not springing back, so I was fiddling with this thinking you must be able to take this off without taking the back off ,as the screw is in a really crap location.
So in the end I had to pop the two top screws outside of the unit and the 6 screws at the front, 3 left 3 right and the unit pops out of the box, that enabled you to undo the 5 screws on the metal box that stopping you getting to the dam screw, it actually does not take so long.
Just if you change it, put it on and the move it up or down to see if it turns the micro-switch off before tightening it up or you will get it all back in the box and it was not set right so all out again.
I am going to play with the one I have pulled out as there is a silver ring that I think you maybe able to undo the set screw there and somehow twist that ring around to get some extra tension.
And before you do anything put a bit of oil on the shaft as that's maybe all you need ( probably some old techs will have a chuckle about that "you took it all apart, when all you needed was a bit of oil :-)) " )
Send me a thumbs up if that solved your problem.