I have a Victron Multiplus and everything on the inverter side works well. When on generator or grid there are no polarity issues. When on inverter alone I have the non inverted outlets showing reverse polarity Neural to Ground on the non inverted outlets is 1.5 v. N to G on inverted outlets is 75 mv.
At least one other user has the same issue according to my installer and he has checked the wiring throughout.
You don't say what the G to H or G to N voltages are. You don't have reverse polarity unless the N has mains voltage and the H has something close to 0.
A diagram would help.
I'm making an assumption that your "non-inverting" outlets are connected to the shore/generator up stream of the Multi. If so, what you measure on these outlets can have nothing to do with the Multi.
When grid/generator power is missing, those circuits might not have a G to N connection because their feed does not exist. So you may be measuring crosstalk between the live inverted wiring running in the same bundle. You can turn the inverter off and see if that voltage goes away. If it does, measure the resistance between G and N. I would expect it to be a high resistance. When the shore/grid power is present, there should be a low resistance between G and N.
It is common for some voltage difference between G and N due to voltage drop in the neutral from the loads.
When inverting the Multi, it makes a G to N connection internally so that voltage will be very low even when drawing lots of load current.
