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Hello, the thermostat is definitely bad, it has a short circuit in its printed circuit/ display board. That is why it is flickering, and draining the batteries.
Tell me please if that looks like the manual for it.
I can help you select a new thermostat if you can tell me a bit about your system.
Do you have a gas furnace inside the house, with an electric cooling unit outside the house that does not run in the winter only the summer?
Are you handy with electrical wiring, or will you be needing to call someone to replace the thermostat.
Let me know, we can go from there without a time limit.