You can easily take the switch apart, just remove the tape. Maybe you have some oxidation or something under the dome.
I’m not sure what you mean by the metal spacer between switch board and tailcap.
I’ve tried taking the switch apart already, and couldn’t see any sign of oxidization either on or under the dome - I really can’t work out what the problem is there.
The spacer is a slightly bent flat ring that was seated between the switch board and the rubber boot with the ‘nubbin’ in. I haven’t seen any sign of one in the FW3A dissassembly videos so perhaps it’s a new addition?
I wonder if we can get more resistance in the switch by taking off the spring-steel dome on the switch and bending the 3 wings slightly inward.
I have an FW3A with the tail switch held in place by a retaining ring. It works only if the retaining ring is slightly loose; the Goldilocks position. If I tighten it all the way, it ramps to high and stays there - clicking the switch has no effect. If the retaining ring is too loose, it won’t switch on.
Took my switch retaining ring out along with the Oring holding the clip from slipping. Left them out! Clip moves a little, but it doesn’t bother me as much as the switch not working 
I wish we could get whoever does QA/QC at the manufacturers’ site online here to talk about what to look for where.
Stuff gets by them that ought to be resolved by attention early on in the production line.
Another post commented the FWxx design requires especially high tolerances. Perhaps they are higher than Lumintop, or most flashlight manufacturers, can consistently achieve.
And we’re hardly the most tolerant QCQA bunch, now are we?
Is the edge of the rubber piece neatly fitting down in its groove?
They test the prototypes, but after that they may only test some random lights coming off the assembly line (my guess). They definitely don’t test each light, if that’s what your thinking. The person doing the testing probably doesn’t speak English so it would be very difficult to ask anything.
I am in need of a couple of the white o-rings that sit above the pocket clip, 1 is broken and another is close. Is there a source for them? I really do not like it when the clip spins and the tailcap is tight.
I’ve also had a couple of those white o-rings break. Managed to find a replacement black o-ring among my miscellaneous supplies that fit. But I agree it would be good to make replacements available.
O-rings are not special, try your local hardware store or maybe ebay. Maybe even a rubber band.
Are you sure about that little white one? None of my assortments even get close to an band diameter that small.
When I bought the smaller battery tubes, they came with a couple of white O-rings for each.
I picked up an 18350 tube and it came without one. That was how I broke the first one.
I bought my from Lumintoplighting. Where did you get yours?
Direct from Neal.
When I bought some deep carry clip from Neal, I thought it was supposed to come with some white O-rings too but it did not. Either I got lucky with Lumintoplighting or Neal just doesn’t put them in the box.
No O-ring with deep clip from neal also. I guess it only comes with the short tubes?