It sounds like a stuck button on the TV. Probably a channel button. Try tapping on each button to get it to stop. If it does, then use the remote from now on. If I was repairing the set here at my TV shop I would open the set, turn it on, and unplug the buttons while it is running. If it stoped changing channels then I have the proof that it is the buttons causing the problem. If it did not stop with buttons unplugged then the tv would need a circuit board. The Brand and model number posted would let me look at the schematic.
Steve
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