Don't know that you've sloved the R91 problem xlcel101x...
i experience something similar tonight. The R91 showed resistances far out of line with my intended build(s).

This on the DNA (VS) and Ohm Reader.
Rebuilt several times to no avail. Finally, adjusted the 510 pin, getting a resistance close to my goal. (Curiously that was "0.15", as I wanted to get close to another tank built to 0.17.)
Once I was setup and back in business I realized something else was likely going on: the R91 base was not screwed down/in completely.
Worth a try?