Surron Ultra 2025 brakes stuck on

Sons bike, rode yesterday and tipped it over on firm grass flats, and threw a H code but brakes then became stuck. He rode 8ks home with back brakes stuck on.

We don't have a brake bleed kit.

Anyone know why this would happen from just tipping the bike?

And any solutions.

Googled of course the brake bleed and checking callipers but I've no idea what I'm looking for and son is not the pull apart and figure it out boy.