How to open a Fenix PD20

I bought a Fenix PD20 and want to put a GITD O-ring in it. I'm also looking at maybe doing a forward clickie, but I can't seem to get either end open. When I take the head off the battery compartment there is a small line where it's obvious the head is put together but I'm unable to break it loose. I don't want to damage the finish.

The clickie is likewise seemingly permanently attached to the bottom of the battery tube.

Is there any way to break these loose? I've tried using a rubber bottle opener mat but it didn't budge them. Yes, I do open jars for the wife easily.

Are the threads reversed on these or something? I have tried both ways.

put head and tail in ziplock bag and boil or put in hot water for a few minutes then try again , learn from these mistakes