I have a 3 phase system with six 10 kVA inverters (2 inverters per phase). I have a problem that the inverter settings in VE Configure are set to Inverter output voltage at 230V for all inverters but I keep noticing that when the systems switches to Inverting mode, because of out of range voltages from the grid, two of the phases supply 245V instead of 230V that has been set. One of them actually starts by supplying 245V and then supplies 230V. Could anyone have an explanation for this?
pls check the grid settings, or better post them here 
How does the system behave if you disconnect all AC IN (switching off the breakers)?
As long as the AC IN is completely gone the system still tries to synchronize.
It also could be a problem with a missing N on the output.
I’d try setting ac-high connect and disconnect both 20v lower on all 6 inverters.