Its most likely some automation rule or smartapp which is doing it (it can’t change by itself). You can review a list of SmartApps using your thermostat from the IDE → My Devices → Click on your thermostat → Scroll down to the bottom of the page and see the list of SmartApps.
You try to press the “black reset” button as shown in this post to reset your thermostat.
If that doesn’t fix it, you can also try to exclude, factory reset (see the bottom of the first post here for instructions) and then pair it again with the hub. This will also disconnect all existing automations and smartapps and should give you a clean start.
Also it help to pair with the C-Wire connected on this thermostat as it puts the thermostat into active repeating mode rather than listening mode.