ok, I think it’s somewhere in here
To snag the ring if it’s gone past the end of the threads — because the driver isn’t quite thick enough or the notch it sits in is cut a little too deep, same result —
— use a needlenose plier in the holes in the ring, point the lens up, gently rotate the ring counterclockwise until it engages — falls onto — the threads then back it on out slowly. Don’t twist against any resistance, you don’t want it cross-threaded. Then you can add a little bit of something to the edge of the driver to thicken it up a bit before you try to turn the retaining ring tighter again. But that’s all from memory, this has happened off and on on a variety of pills/lights. Best wait for someone with a better memory. Oh, I said that already (grin).