Was able to fix this.
This was caused by a faulty fade briefing icon that is used only in this mission.
Actually that is very strange, because i did not changed anything in the briefing icons and i did not have problems in my initial playthrough either.
But nevertheless, i fixed this and this mission is working, now.
Unfortunately the file is in the big effects package, but because Knossos want to upload the whole modification for the new version, i have to reupload the whole thing again anyway.
But the file for the manual download was already updated @ModDB
You can download that one and put the VP into your "StormFront-2.2.1-B-Nova" folder in Knossos, wait for the Knossos Update (which will cause a complete new download as it seems) or you simply extract the attachment into the mentioned folder, which only include the fixed file in the required folders.
The attachment can be used for the wxLauncher version with the Nova-StormFrontSaga folder, too of course.
Well, actually i hate to reupload 350+MB for a small 6 KB fix *sigh*. But it is unlucky this time, because most of the fixes i had to do in the past were table or mission issues, for that i already use small individual packages.