Please explain how you aren't convinced that it's not broken.
I am not trying to argue, but these are generally pretty indestructible. Of course anything is possible.
It would be odd for someone to try to glue or loctite the switch closed, but again, stranger things have happened.
We are simply trying to help you troubleshoot here. Photos might help.
When I tighten it all the way down the light turns on. Loosen it slightly and try to push the rubber cap for momentary absolutely nothing happens. There is ZERO movement when pressing down on the cap....
The amount of travel in the standard stock Z41 is tiny.
In fact, without batteries loaded, I can hardly detect it (because there is nothing for the spring to push against)
Even
with batteries loaded, I'm guessing the distance moved by the switch is maybe a millimeter (?)
If you loosen the cap too far (not far at all) , you will be locked out.
Are you using this 6P with a stock P60 lamp assembly ?
What is the *smallest* amount that you can loosen the cap ? Can you get the lamp to "flicker" (barely closed) and if so, what happens when you depress the button then (ie, will it go from flickering to constant on) ?