The nemmy clones have been a little notorious for this as far as I've heard. A lot of times from the gunk build up on the threads. Soap, water and a scrub to clean the threads up and then some nolax for the threads should do.
Good of you to bring this up. If anyone using
mods get a sudden jolt - their button / switch becomes extremely hot, I mean feels suddenly really really hot - like makes you jolt - it could likely be from arking. Check the connections and
coils or in some cases gunk in the battery threads. Potentially dangerous stuff