When was the last time, you cleaned the 510 connection on the mod, and the tank? I clean the connections once a week, at least every other week. Put some alcohol (90%+) on one side of a q-tip clean the contacts, use the dry side to wipe the contacts dry. Let it sit for a Minute, in order to let eventual left over alcohol evaporate. Re-assemble.
Is the coil your own build on the RBA, or are you utilizing replacement coils? With a replacement coil, I'd switch it out with a new one. With your own build, I'd re-check the coil and it's contacts on the posts. You can cut the wire, when you over tighten the screws.