Electric pressure washer is pulsing forever when handle is released

Hi!

My power washer (Michelin MPX1900) is having this issue :

1) When I pull the handle and use it to wash, it works fine, strong and steady pressure

2) As soon as I release the handle, the pump just goes “womm womm womm womm womm womm”. It just builds pressure every second and loop forever. I have to turn it off when I release the handle for more than 2-3 seconds because the noise is annoying and I feel like it’s going to break at some point.

3) There is ALWAYS water coming out of the end of the gun when the handle is released. It is low pressure water and the flow is steady (there is no difference if the motor is pulsing or if the switch is “off”). Should there always be water coming out?

Do you guys have any idea?

Thanks!