I just got out my second aegis solo from ejuices to try before putting it in my stash and the threads on the battery compartment are bad. It turns 1/4 turn but won’t tighten. I tried a cap off of another one and it won’t screw in either. I strongly suggest everyone try theirs out before putting them away.
I had one like that. I took the battery out and took the rubber seal off the cap. Then it was quite loose but at some point it came to a hard stop. Discovered that if I pushed down on the cap while I turned it would go past the obstruction. I kept turning it on and off and after a while it got better. Some tiny metal shavings came off. I also poked around with a dental pick. It's fine now.
Whatever obstruction I had was fairly small. Yours might be larger or a really messed up thread. Worth trying before you send it back though.