RC-2000 internal temperature sensor accuracy

Have any OmniStat2 owners found the internal temperature sensors to be wildly inaccurate?  I have both a RC1000 and RC2000.   Have compared each to 2 different cooking thermometers and have to set calibration offsets.  The RC1000 reads 3 degrees too high and the RC2000 reads 6 degrees too low.
 
Thanks.
 

I have four and they are pretty inaccurate but if you calibrate them they stay accurate. You would think Leviton would do a better job at calibrating them, but I guess not.

What method did you use to calibrate it?

I bought a lab type digital thermometer which are like $15 and positioned it just on top of there OmniStat2.  Then, over time, I tried various adjustments until temps matched the closest. It took a few days for each one. 

I'm still doing some similar testing. Not sure yet but what I think I'm finding is that the omnistat internal temp sensor is extremely slow to respond to temp changes.
I have a theory that if house would stay exactly same temp long enough it would match my other thermometers.
It has been difficult to maintain temperature during winter here.

Like i said, set the calibration thermometer on top of the OmniStat2 for several hours so they both get the same temp. Then every few hours adjust the OmniStat2 offset so that the two match. Eventually you will be able to get the two to match pretty close.