Switch lite - dead after water contact

Our son just dropped his switch lite into water. It instantly turned of. I just gave the main PCD a bath in isopropanol to clean it but its not turning on again.
I connected USB charger and reading is 15Volt and 0,46 amps. If i disconnect battery its down to 0,15Amps.

So where to start with diagnosis here? If it switches to fast charge this should be fine or?

Have you got pictures of the board? Check for corrosion especially ribbon cables and connectors