There is no logging at this point, but by debugging UE4-EditorCmd I found out that the asset causing this issue was “InvalidLightmapSettings”. Since this is provided by UE4, I followed the hint in the issue I posted to completely rebuild the engine in a different folder (deleting intermediate etc. did not help). With the new engine folder, the Assertion no longer occurs. Sorry for the noise, as this turned out to be not nativization related. From now on I will rebuild UE4 in new folders even for minor releases.