I had to buy a large tweezers and tighten all the retaining rings on my FW3X V2s.
A few days ago, the switch started acting up on my FW3A bare. Today, I took apart the switch to find pieces of what appeared to be the flat black rubber spacer; not the nub. The pieces were not from the spacer in the light. I used canned compressed air to clean the circuit board mounted switch. The switch is now back to behaving.
Wish I would have checked the switch before I originally tightened up the associated retaining ring.