I personally have not used a coil in a tank above .5 ohms for a very long tine, but what i can tell you is that IMO that is a coil issue, i have seen my fair share of faultly manufactured coil builds that read differently than they should, or just don't work period. I am not a huge fan of kanger, i have used them with no issues, just prefer other subtanks.
My suggestion is like mentioned above, grab another coil, run that one and see what it does, if that works, great. If not, find another tank and put it on there to narrow down whether your box isn't performing correctly or whether its just the coil (which is my guess).