| Is this something that just started happening, or has the system always done this?
In defrost mode both units will run together, but you'd notice the outdoor fan stop running during that period, and it would only last a few minutes. There really is no reason to have both heat sources running together, and there is debate on whether this might cause longevity problems with your compressor. So yes, I would correct the system from running both at the same time, except during defrost of course.
Before you go swapping out tstats I would try to understand what the system is doing. |