Pump blows instead of sucking


We have several Dobot Magician for schooling purposes.
With one of the systems there is an issue with the pump.

The pump is blowing instead of sucking.

I have tested other pumps on de Dobot, they all give the same result.
The pumps operate normal on other dobots.
Hence, the issue seems to relate to the dobot.

How to fix this dobot?