Tail cap came unscrewed while assembled
Well, ain't that a &!&!$!! Maybe it is because I have one of the poor fitting gaskets, but the tail cap came unscrewed while I was trying to disassemble the flashlight.
I was able to get it undone by degreasing the tailcap threads and applying some threadlock (actually just superglue...I couldn't find my blue threadlock).
But it seems like this is an area for design improvement. Maybe using a reverse thread on the tail cap base or provide some holes on the inside of the tailcap so you could use a pin spanner?
Is this a good question?