The screws with
the buggered-up threads WILL unscrew out so you can get the ring
terminals
on if you force 'em.

No they won't. I learned the hard way with a previous GFI. The screw
goes into a loose square nut plate inside to clamp the wire. If you
turn it out, thinking you can force it back in as you suggest, the nut
plate falls loose inside. I tried wiggling to get gravity the get the
nut plate back in position so I could push something in the terminal
holes and get the screw back in. There are still pieces of GFI in odd
corners of my shop after I tried the next alternative of smashing the
bloody thing with a hammer.

--

Roger Long