I had a similar experience with the Subpar Mini...
I HATE Kangertech with a PASSION!!!!. The Subox mini ( or the Subpar Mini as I call it) was my first vaping experience. It was awesome for about 18 days. Then I went to charge the device and noticed that the USB charging port had broken off. IT BROKE OFF!!! it was rattling inside the case. After talking with the B&M store where i purchased It I decided to just ignore it and buy an extra battery and external charger for convenience. Three weeks later, the tank started exhibiting the 9.99 ohm error. I borrowed a tank from a friend and it works on the mod, my brothers tank works on the mod. just my tank doesn't hold a stable resistance. I tried all the fixes I could find online and even had an engineer try and figure out the problem. I documented everything and contacted Kangertech USA service by email. I gave them pictures, copy of receipts, Authenticity info. I didn't receive a response to my email for 4 days. Finally, I got tired of waiting, I found a their phone number and contacted them. Their response was to send me a form letter telling me to send them everything I had already sent them except the physical device. I get the impression they didn't even read my email.
Vaping isn't a hobby we do when we have time. These companies need to realize that we use them ALL DAY LONG! Mailing in the device requires me to buy a second unit. I payed extra at a local store expecting that the added cost meant added service, just like other items you buy. Nope! Screw Kangertech and other companies that take our money for their defective crap and then not take any risk or responsibility themselves in the repair/service/replace warranty process.
MY SOLUTION
I purchased another device that does not have the Kangertech logo on it and I will NEVER buy another Kanger product again.
Problem solved (I cut and pasted this from anther reply)