Just ran across your post. Got the exact same issue. Don't get the praise the device received in reviews. What's more is that when you select "Old" it will display the old resistance but adjust the output voltage to the one it just detected, regardless. So the option is basically useless, as it will always fire at the detected resistance anyways. The only way I was able to stop this (and the stupid pre-heat punch you have no control over), was to use a TC mode (I chose nickel) for regular kanthal coils. The set temperature shouldn't have any impact but I set it to the highest value anyways. Since kanthal resistance increases way less than nickel with heat, the mod will simply fire at close to the (TC-)selected wattage. It still asks about the atomizer from time to time but it's become tolerable (maybe 2x a day instead of what felt like every third button press). If it asks, it does still detect arbitrary resistance values but they have no influence on the output power for some reason (you should think that if it erroneously reads too high a resistance, fires, realizes the resistance under load is LESS than the initial value it would quit firing in TC but it just doesn't).
Obviously this workaround only works with a non-TC coil and am not planning on using it for "real" TC after how poorly it performed it simple wattage mode..