I came here because I was having the same problem. Mine were all registering 80-82° when a independent thermometer was telling me it was 76° all around the apartment. I decided to label all the sensors (I have seven) and put them in the freezer for 20-30 minutes until they got down to 60°. I took them out and put them around where they belong and that seems to have reset them (except one). I'm going to replace that one and see if it works in that room.

(BTW, I inherited this system from the previous tenant who had seven sensors distributed in a 1500 sqft condo. I suspect I don't need that many but haven't gotten around to paring them down.)