You might be able to tell which it is just by looking at the threads, A magnifying glass would help. See if the cap threads are damaged. Harder to see the threads on the mod. You should be able to see what’s up though, it would take major damage to the threads for it to spin freely.
Take the o-ring off the cap and take the battery out and see if it threads in at all.
I guess it’s also possible that the body of the mod is cracked allowing the hole to widen up.