Welcome and glad you joined.
There a quite a few causes that result in the stripped thread problem you defined.
Might try a 510 TO 510 and or EGO ADAPTER :
http://www.evcigarettes.com/eleaf-510-to-ego-thread-adapter-connector-by-ismoka/
510 to Ego Adapter
510 to eGo Adapter - $2.49 : EasyVapors.com, Electronic Cigarette Cartridge and Cartomizer Refills ELiquid
Often, this improves connectivity, and have found this works for me.
Cons:
1. Adds height to your mod. However, the flip side is I can get my fingers on my RDA bottom casing and quickly unscrew the RDA if I wish.
2. The design of most 510 - Ego Adapters has meager/if none adjustable center pin capability.
"I would of gladly paid a little more money if I could of ordered the Ismoka 510 - Ego Adapter with an adjustable 510 to 510 center pin.
REF:
HELP! Eleaf iStick 100w and Aspire Cleito Tank
The big adapter Pro is, it is a sacrificial lamb, if you strip the brass threads, just replace with another adapter.
Strongly suggest you take you equipment to a B&M vape shop or a garage mechanic and ask for assistance.