Loose battery connection perhaps? Probably worth taking it out and putting it back in again and seeing if that solves it. The old turn it off and on again!
I think you’re right with it needing the battery disconnecting and then connecting again. I’m going to do that certainly before I go on holiday for two weeks and leave the car. I’m not sure if the beeping is enough to drain the battery on its own, but I cba to find out the hard way :-D
Loose battery connection perhaps? Probably worth taking it out and putting it back in again and seeing if that solves it. The old turn it off and on again!