I just found a workaround. T3D can still be imported. The trick is to type *.* as the file name and press enter so the t3d files show in the file browser. So in the end it’s just a minor ui bug.
Just one more thing. Another no-crash scenario:
select all items in the default level except the first one in the World Outliner,
export selected to t3d,
import t3d back into level => no crash
One more workaround for the default scene crash. Remove some lines at the end of the t3d file that refers to the level map, before:
Begin Actor Class=Minimal_Default_C Name=Minimal_Default_C_2 Archetype=Minimal_Default_C'/Game/StarterContent/Maps/Minimal_Default.Default__Minimal_Default_C'
End Actor
End Level
Begin Surface
End Surface
End Map
One last workaround for UE3 T3D files is to remove all lines that look like
xxxx=BrushComponent’yyyy’, I use a regular expression in Notepad++ to remove all the lines with find and replace ,"^\s*\w*(\w)=BrushComponent’.’.*\R"