Thermostat temp sensor very erratic

I think this product may be a complete piece of junk, by design. Somehow the temperature can fluctuate from 65F to 71F within a few seconds, then back down to 67F after the furnace goes on for a minute and stops.

This used to happen when I first got the device 2 years ago, then seemed to be ok last year, but it’s doing it again.

Is this defective, should I try getting a replacement or just buy something else that works properly?

I have had my Wyze Thermostat installed for two years and have not experienced that.

Is it possible that the thermostat itself is getting hot internally during the time that it is fluctuating due to some sort of electrical feedback from the furnace on one of the wires?

Do you have a way to measure the thermostat surface temp when it is doing this? Possible an IR Thermometer?

Mine just started doing the same thing. It causes my thermostat to turn the boiler furnace on and off within a minute many many times through the day. Now, there was work done on the boiler a few days ago and the thermostat has been acting like this ever since. Wires swapped? No idea. I’ll have to ask them when they come back this week when they replace a bladder.