Current in cooling water

Hello guys. I have a problem on my setup.
I can feel somme current in the cooling water of my flipsky vesc 75200.
When sucking water with my mouth to prime the system, even when the motor is stopped i feel a tickling on my tongue, akin to licking a 9v battery.
The efoil runs alright though.
It was not happening before, and is a bit worrying.
I was running a 6384, and if I disconect the motor the current in the water stops.
I tried another motor (65161) and it is still there. But a bit less.

Do you have any ideas ? Just esc malfunction ?