To anticipate it, the installer yesterday checked the wiring. From the house connection via the MultiACin via ACout to the loads, the same cable colors are never crossed. 35m 5x16mm² underground cables were laid from the house to the MultiPlus and back. Since no error was found, Ve.Configure tried all 6 ways of assigning the phases:
1-2-3, 1-3-2, 2-1-3, 2-3-1, 3-1-2, 3-2-1 for all there was a phase rotation warning if the MultiPlus tried on the grid back.
Three-phase motors have the correct direction of rotation both in inverter operation and in mains operation (manual switchover possible via switch). We have no idea