Thx to anyone for trying to solve this error, in advance!
like said the editor works when network is turned off.
but chaning the defaultengine.ini only works for me if i change the line:
bAllowNetworkConnection=True
to
bAllowNetworkConnection=False
(under c:/users/$myusername%/appdata/local/UnrealEngine/5.1/Config/)
does anyone have further information on why it works like this, or maybe if there will be a fix / an update soon…?