If the parking brake isn't fully retracted, it seems very reasonable that the alarm is sounding all the time, since the risk for overheating the brake must be imminent. That the car is able to move doesn't say that the parking brakes aren't partially applied.
The electric system, like everything else, is continuously updated by Volvo. Your owner's manual may not reflect exactly your model, since there are updates that are put in production in the middle of the model year.
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