Yes you are shorting out somewhere, the question is where, and why is it intermittent? I'd start by taking a very close inspection of the build, I would put it back on the ohm's reader after cleaning it and see what happens as you test fire it. It could be as simple as one leg of the coil not being affixed correctly or something as complicated as the mod having an electrical fault. I think the former is far more likely, but if you check your build out thoroughly and test fire it a bit on the ohm's reader, that should give you a sense of whether or not it's the mod at least. It could also be an intermittent connection issue so I would clean your 510 connections (both of them) to see if there is something interfering with a solid connection that needs to be cleaned out or otherwise addressed.
Best of luck, I'd imagine it's probably a build issue, that seems the most likely culprit but it could be something else.
Anna