Charging problem machine cannot hold battery and charger

Hi guys i have this funny laptop and I'm trying to repair it.

The laptop got a small liquid damage. when it came it wouldn't recognise any battery and it was working fine only with the magsafe connected.

After cleaning any suspicious rusted component with alcohol there is what i got.

1 if the battery is connected to the board the devices work fine as long there is charge but the magsafe is not charging (no lights) if connected.

2 if the battery is disconnected from the board after 5 minutes(only first time then works instantly ) the laptop works fine with the magsafe connected.

3 if the mag safe is connected and after powering on (like point n2) I connect the battery on the board, the laptop is working and the battery is charging as in normal condition.

3a if i disconnect the mag safe from the previous point and try to reconnect i wont charge and the light remain off.

What i have tried:

SMC and PRAM reset

New charger

Replace the mag safe connector.

I'm waiting a new battery in order to replace and try but I don't think it will solve the problem.