Hi Path,
If you have a multimeter, try to prove continuity, and that the basic centre pin will fire a most basic old flash.
-Maybe with a film camera and an old manual flash.
The Japanese hot shoe design was a bit of a mongrel in my opinion, too weak for the flash unit weights etc.
Also the flash clamps are a bit disconcerting because in mechanically tightening the flash body
they unload the contact pressure on the electrical pins !
So we see reference to "wobble the unit till it connects" etc
Years ago I purchased the real Pentax parts. They were expensive, but they still work OK
https://app.box.com/s/3t1h7jpcpdxg52dvpc6yku7vw9rlcp0j
Edit, sorry I posted before reading that you fixed it.
Anyway the "not pushing forward" against the varying springs is another design deficiency in my opinion.