@debaserrrrr STOP do not take the air apart unless you are very skilled with electronics. Did you try cleaning the battery contacts?
Excellent advice, IMO on the first part. Even if you don't mind 'killing' the warranty your chances of finding something mechanical you can deal with are slightly better than your chances of getting it back together without further problems IMO. And I've been there. Your call, but IMO sound advice does not include taking it apart.
I'd be very careful with the 'cleaning the contacts' idea as well. Good advice for fixing flashlights and such, but here we have GOLD PLATED contacts specifically to remove contact problems from the potential mix. Gold is the idea material for this (excellent conductor, not corrosive, very soft) which is why it's used extensively in high tech electronics. But, it's very very thin. If you scratch it and 'break the surface' Oxygen and water vapor will make it though the breech and eat the base material out from the inside, like dry rot in your house. Best avoided, don't touch the Gold part is my advice here.
Air is very sensitive to battery contact, using any other 18650 is asking for trouble IMO. Even 'better ones I found on the web'. Airzer isn't stupid or incompetent. If a better, cheaper 'battery' was available they'd surely use it? I've experimented a bit with this, some cells (the real name for what we mistakenly call 'batteries') are just enough larger to bind up slightly in the tube so they can lose contact as things move (return spring not strong enough to overcome it). Some were enough shorter to cause resets if you bumped it hard.
My advice is 'stick with the factory 18650s exclusively, be careful of the contacts. Including the spring loaded pin that makes contact with the end cap PCB......I had one fail along the way. Fortunately I had one I could take out of my scrap unit, the one I broke taking apart......
If it defies you, send it in. Let the experts with the tools and parts do it, they know what they're doing? If you cleverly bought from Randy at PIU this is so much easier it becomes a 'no brainer'.
Regards to all.
OF