I see others have already opined correctly SLX, and you also seem to have it working now. However, pls note ~ it is the 'locking ring' which is reverse threaded, not the switch unit as a whole.
When I received my Paps v3 (not this Lux v3), it came in the 'open' position. The locking ring I mean. And the bloody thing wouldn't rotate. Left it in the deep freezer for 15-20 minutes and voila!
Infrequently many of my other stuff get stuck likewise as well. Especially the K'fun tube sections. Straight out of the deep freezer - one or two "sudden twists" - and they all start falling in-line, start behaving!
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Tons of devices here, many months of use, I have never ever had to use any rubber bands, gloves, drawer matts, balloons (yep, heard that too!) etc. It's always the freezer which does the trick, for me!