Why does the temperature target change after I set it?
A changed target does not prove the furnace has failed. Look for a schedule, hold or away label on the normal screen. Use the thermostat instructions to check what it means. If another person or app has access, find out what changed before buying a new control.
Keep a simple display history
Write down the target you chose and the target shown when the problem returned. Add the time and whether the room reading changed too. A photo can show if the target changed or the system failed to reach it. Stay out of installer menus and wiring terminals.
Use the exact screen text when you call. Do not guess what auxiliary, emergency or hold means on this model. Features vary with the control and heating system. A label on one device is not a rule for another.
Agree who may change the settings
For a North Naples home with an owner, resident or property manager, confirm who may use the control or app. Say if the equipment is shared. Check whether settings may be changed during the visit. Never put account passwords in a repair request.
If the owner is away, get consent for the specific work rather than assuming a caretaker can approve a new thermostat. Choosing a room temperature and changing equipment setup are different decisions.
Check the fit before buying a control
Ask what fault was found. Does the proposed control work with the installed system? Find out who will check it after the work and explain its use. If it responds correctly but the home stays cold, the heating fault still needs checking. A new screen does not prove the comfort problem is solved.