Hi @wbarsuhn, welcome to the Cayenne Community.
I think you're onto a legit bug here. I set up a similar Pi to what you've described here, and while I'm not seeing one of the trigger ranges stuck between such limited values of 71-72.5, I'm not able to get any of my DS18B20 triggers to retain a change to the Min/Max setting, which is ultimately your problem here.
I don't want to make things worse for you, but do you mind confirming by taking one of your triggers that has the full range, and editing it slightly? For example, changing one with a range of -67 thru 257 to -66 thru 256, then saving. I'd be interested if those values are retained for you when checking after saving.