Multiplus remote not working with cerbo GX setup

Hi,
I’ve found contradictory answers so I’m not exactly sure what’s the expected behavior

I’m trying to install a physical switch to easily turn off the multiplus from a distance.
I wired a three way connecters to the H connector as per the manual instructions, and no matter what I do I always en up with 230v in my outlets (in charger mode I get like 10s of power and then 10s of blackout ; In the two other mods I get continual proper 230v)

I have no idea what’s going on here.

Is it possible to make a physical 3 way switch work when the Multiplus is connected to a BMS through a cerbo GX ?

Thank you