Why does station change when unit is turned on?

Why does station change when unit is turned on?
I've had this HD radio for several months. I really only listen to one station, preset HD01. For the past two days, every time I turn on the radio it starts playing HD02. I have to manually push the - HD Search button to get the device back to HD01. It also takes longer for the audio to start playing than it used to. No one else is using the radio. What the heck is going on here?

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