Old Lady Adler 467 373 Thread Problem

[LeoWe]

Hello, I’ve received an old lady. She spent 10 years in a basement. It’s an Adler 467-373 that comes from an upholstery shop.

My problem is that it frays the upper thread, and I think the timing is off.

I cannot find the screw on the shaft to loosen the hook on this model.

I’m sure you can help me. I’ve attached a few pics. 
 

thank you 

Leo