That worked for me! The Wd-40 Specialist Water Resistant Silicon Lubricant, carefully joining the tip of the straw at the junction of the collar with the front of the valve, and also tapped the collar against a solid surface all around (sauce jar style) and now - not to deviate the thread - nothing seems to be wrong with the internals; ingenious system, several gears and I suppose when one reaches it's cycle position it re-routes the water to the back up jet. All gear spin freely, yet my backup valve does not create the opposing water jet anymore...
What did work for me was WD-40. I squirted it around the collar and let it seep around for a few minutes. Of course, then it was too slippery to hold on to.... So I got a t-shirt rag and tried to get a grip on the collar. Turn, turn, wipe, wipe and finally I've got a good grip and off the collar turns.
I was thinking about the same options everybody else has mentioned before I tried the WD-40. Didn't really think it would work on plastic, but it did.
YMMV. Good luck!
It is definitely an extremely poor design!!. Before I used the hot water I hit it with a hammer many, many times after I applied WD40Got news for you, it does not always work ! Finally went up to 200 F water, still no help ! Extremely poor design.