I have exactly the same problem ( including the nav radios) and it spoils an otherwise excellent sim.

I have the electrics set as suggested but no matter what I do it happens on every flight. I have noticed that sometimes the 3 control motors switch off when power is lost.

I put a ticket in to C.S. and got a response "Thank you for your issue report, the issue is forwarded to our development team for consideration. "  on 3 July. Not really sure what that means - hopefully it hasn't gone into the "too hard basket". I will post any response here.

If anyone has a suggestion I will give it a go.

:(