I get home last night and it's hot. Hmm so I walk over to the thermostat and it's on 70 but says the homes temp is 55. So I Mess with it put in new batteries. And sat it as low as it would go 45 degrees within 5 minutes It said it was 24 degrees in the house. Realistically it was almost 80 probably. Would this just be a faulty thermostat? Or something else?