I need to have 23 degrees in my house or my wife will turn on baseboard heating until the house reaches 23. She doesn't understand why the nest keeps lowering on its own and quite frankly i don't either. Having installed hundreds of thermostats as an electrician for over 30 years, I've never seen one that will not maintain a temperature. Hold only lasts up to 24 hours and eco mode is capped at 21 degrees. I find it hard to believe that a thermometer cannot maintain a temperature. At this point I set an alarm every day to reprogram the nest for short holds, hopefully I don't have to get the honeywell again, I really like the look of the nest.
Sorry to hear about the trouble. I wanted to follow up and see if I could be of any help. Do you mind me asking if you have a schedule set up? I found an article that could be of help. Please let me know if you are still having any trouble from here, as I would be happy to take a closer look and assist you further.