Final Cut Pro X "Camera Clips Selected" / "Kamera-Clips ausgewählt"

Final Cut Pro X did crash a few times during importing a large number of SD cards and moving the event to an external drive.
Now there are 8 clips in my Event Browser showing a little camera symbol.
I can't analyse them because of a message:

"Kamera-Clips ausgewählt" (I have the German version of FCPX.)
"Kamera-Clips können nicht verarbeitet werden. Sie müssen zuerst diese Dateien importieren/erneut importieren, um sie zu verarbeiten."

I found the proper original term by guessing:
"Camera Clips Selected"
"Camera clips cannot be processed. You must import/reimport these first in order to process."

These clips are only shown if the SD-card with these clips is inserted while FCPX starts up and stays mounted.

Problem is: FCPX doesn't do anything when I select these clips and import them because they are already imported.
The help-system doesn't even know the term "Kamera-Clip", so it is either inconsistently translated or there simply is no documentation what this is and how to deal with it.

• Same error message in english, similar issue, no solution