It may be there is a bad electrical connection somewhere. Could be a bad or loose coil, or maybe the 510 connection is dirty. I make my own
coils and I've had this happen when a deck screw was loose. The connection goes away then comes back causing the
mod to think there's a new coil.
If it happens after 5 drags every time there may be another cause though. With a dodgy electrical connection it would more likely be random.