The 510 connector threads on the Vamo have been suspect since day one (apparently).
Of the 18 Vamos I have bought, I have had 2 exhibit bad 510 threads. Both were bad on arrival. 1 SS V2, 1 SS V3, both were usable with a 510 adapter installed. Both were replaced at no charge by Fasttech.
Of the other 16, 510 threads have been solid. (Wife and I own 8 Vamos the other 10 are owned by family members)
The only V5 purchased to date has been flawless.
I've yet to have the threads fail on any vamo that had good threads when received.
That said, verify the 510 threads first thing upon receipt, regardless of the version.
Good Luck