Gus,
If I remember, you indicated that with just water pans, the smoker did hit and stabilize at 250 (or am I thinking of another post somewhere). In any event, I would still try smoking another butt, same weight without the water pan. Call it a test.
I never use added moisture. And I let the meat, be it ribs or butt, sit outside of the refrigerator for at approximately 30 minutes with just a dry rub before it goes into the smoker. Outside of one ruined butt (over smoked, but not overcooked) I have always gotten a nice juicy product with good bark. And I shoot for an IT of 190/195, which is my preference.
I have had butts within just a couple of ounces of each other vary in cooking times by as little as 30 minutes to as much as 2 hours. Maybe my probe was sitting in fat rather than meat from smoke to smoke. But they were all good. And my brother (model 3 owner) uses no water pan and relies only on IT, does not monitor the chamber temp as it is going to do what it does with or without an additional reading, and is having good success as well.
I hope you get this narrowed down.
Dave
I just looked at the Omega PID site. Looks like a good solid unit, although I don't know which model you have. Under the Auber tips and tricks topic, it seems like most folks modify and bypass the stock controller to eliminate the conflict between analog and digital. I definitely cannot speak to that but it is worth considering.