Haven't been able to capture a errant temp yet. However, did find another bug. The thermostat (at least the unit I have) sometimes repeatedly sends the current temperature back to HE (example below).
While that is going on, if any commands are sent to the thermostat, the setting on the thermostat is changed; however, the thermostat doesn't report the changed setting back to HE, so the HE device page is no longer in sync with the thermostat (refreshing the device page makes no difference).
The only thing that puts them back in sync is to wait 5-10 minutes until the temperature reports stop and send a different setting change (different from the one tried above) to the thermostat.
In the example below, I tried setting the thermostat state to off. The physical thermostat reports as being off. HE reports it is still in heat mode.