I just installed my Honeywell T6 Thermostat (thanks @bcopeland for the awesome driver)
As I installed it the foam tape around the wire reminded me of an issue I had with the original thermostat in this particular installation (long before-smart thermostats) . It is on an interior wall and apparently air was coming in from the top of the wall in the attic. Cold air could be felt sometimes at the opening for the thermostat wires. This caused the room temperature to sometimes fluctuate wildly.
So just a note, when installing your thermostat, fill the wire hole with a piece of foam or similar. To stop any possible airflow.