Message 21 <<<<This is not a bug, but this has to do with the to Power-Switches "Copilot AC Instrument Switch" and "AC Instrument and Engine Switch". First one have to be in position "Essential AC Bus", Second to "Essential DC Bus". >>>>
It seems to be a misunderstanding in the past too.
Now "Copilot AC Instrument " connect "Essential AC Bus" position is horizontal; "AC indtrument.." to "Essential DC BUS" is upright, OK
AC Power switch OFF and DC Power switch Battery.
I will try a flight with this configuration
When do you disconnect the AC Power switch, after start of the first engine or after all egines started?