Weird problem. I use a vaporshark rdna 40 with subtank on stock coils and also an aerotank. With both tanks the coils will last fine for about 4 days and then I'll get a burnt hit and the resistance on the coil will drop significantly and stay there. This has happened a number of times on both tanks. A new coil sorts the problem until a few days later. I was presuming a short in the coil originally, but it has now happened a number of times on different tanks. If I check the resistance on another device iy has the same read out. So what are your thoughts? Poor coils, mod problem?