My old old S6 has a retainer ring that just doesn’t stick. It’s like the threads aren’t deep enough for it to bite, and as a result every time I pull it apart the switch falls out.
Any suggestions on how to keep the switch in there?
C-Clip? Solder?
Which threads have gone bad?
If the retainer's threads are just worn out, then you might as get a new retainer.
If the tail's threads are bad, then installing a c-clip would also work (make sure to remove the anodization before installing it).
I wouldn't recommend directly soldering the PCB to the tail as it would probably fail in the long run.