Water Damage Issues. Need Your Help Guys

So, a customer has brought in a water damaged s6. What it's doing is this:

It has no power when not plugged in.

When plugged in the battery will charge 2 percent then turn off and start over again.

I managed to boot it once then it started the cycle again.

I've replaced the battery but the new battery is having similar issues, except with this battery it will charge 2 percent then jump to 99. Again, no power to the phone when the phone is not plugged in.

I have disconnected all unnecessary parts, I've also done a basic isopropryl wash of the board and connectors.

Any advice would be great

Cheers