What is the resolution of the humidity display? In my limited experience with it, it seems to jump in 5% increments. For example in very low humidity situations it will change from 16% to 21% with no values in between.
It is the humidity display that is jumping and not the temp. It jumped back and forth between 16% and 21% multiple times so not even numbers. I have another one of these, the same model, and it will move 1% at a time so I'm not sure what is wrong with the other one. Maybe when the humidity is very low then it has lower resolution. The one that works is in a location with higher humidity.
Maybe this is an accuracy problem. I set the 2 meters side by side for 3 hours and the original meter (bad meter) displays 16% and the other displays 22%. When humidity changes by a small amount, the "bad one" jumps from 16% to 21% while the "good one" will change incrementally 1% at a time.