Thanks for all the responses. I’ll try to cover all the points raised.
1. The paperclip spacer (hat tip to ToyKeeper) was a temporary solution to test the hypothesis that one tailpiece was shorter than the other two. In that role, it succeeded. I’m way too perfectionistic to treat that as a long-term solution. But I do appreciate the links to spacers providing a better compromise.
2. The two “shorter” battery tubes are both shorter in an absolute sense. They are specifically shorter in the section from the end of the battery tube knurling to the tail tip. As well, the length of the threaded section of the battery tube at the tail end is shorter.
3. Yes, I am certain the battery tube is oriented correctly. Still, it’s always good to check the easy solution.
4. I was able to combine sections of the three lights I purchased to form three functioning lights. My issues are: a) the concept of interchangeable parts, dating back to the third century, b.c. was violated, and (on a more personal level), b) if part of one of my lights fails in the field, I cannot replace it with the equivalent part of another.
I do appreciate the opportunity of this group buy, and in no way seek to appear ungrateful, or denigrate the good work done by the BLF members behind it. Honestly, thank you all. My issues are with the execution by the factory—??—in manufacturing tolerances, with the manufacturer—Manker—in assuring a wothy output is produced, and good faith of the vendor—Banggood—regarding the responsibility they assume in making these flashlights available to the end-user. I am optimistic about the resolution of all issues we experience. And I genuinely hope they address these concerns; both for selfish reasons and for the good it will do the community and Manker and Banggood.
5. By way of an update, I contacted heyanquing1@banggood.com and am attempting to have appropriately sized replacement parts delivered.
Pending resolution of these matters, I have friends who want to order some of these flashlights for themselves (because they are not getting mine!)