Battery

Hi, I've got almost new (late 2020) Warwick XL and I've been getting some erratic readings on the Harmony panel recently. When plugged into the mains to give some charge to the batteries it didn't show any incoming charge rate on the screen and also when switching the power off again the engine battery was showing 11.4v when I knew it was around 12.6v because I'd checked it with a multimeter.

I contacted Sargents who said it sounded very much like there was a problem in the fuse box behind the drivers seat. I checked and found the 20amp battery fuse had blown, I replaced it and everything was then OK. My question is, should I now leave it as it is or should I try to investigate why the fuse blew? I'm not great with electrics so it would mean going to the dealer but that's a 120 mile round trip.

Thanks for any help and suggestions.