Minolta srt101 (SLR) trigger jam

I’ve done a lot of searching but haven’t found much regarding film Advance lever/trigger errors. Symptoms: lever will advance once or twice, with the firing sound being a dull “krk”, not the bright “K-chung!”. After one or two advances, the mechanism becomes jammed, and one cannot fire or Advance.
Removal of lense showed that mirror was not flipping up during misfire.
Removal of bottom plate showed that internal mechanisms were not pulling spring fully, which was not cocking the firing gear hammer arm(I wish I knew the nomenclature! See pic.)

Any clues? I read somewhere that the white firing gear may just need lubrication.

Would wd-40 be appropriate for internal SLR mechanisms?

Thanks in advance