I just noticed, that moving those AI_ExePath Components between "root-level" features is not allowed (drag'n'drop doesn't work). I can only move them between sub-features.
I also noticed the following:
In the past I added prerequisites. Features were automatically created for those prerequisites. I moved them inside another root-features.
Now I deleted some of the prerequirements, because I don't need them anymore.
It looks like, everytime I delete a prerequisite, every component of the corresponding feature is deleted - except the AI_ExePath. This AI_ExePath seems to be moved one level up (inside the root-level feature). The sub-feature is deleted only for the first prerequisite I delete. When I delete another prerequisite (which feature is also a sub-feature inside the SAME root-level feature), the AI_ExePath cannot be moved one level up, because there is already an AI_ExePath component. Therefore the sub-feature remains with only on component - the AI_ExePath.
Now the project is messed up, because it contains features which should not exist anymore.
How can I get the project clean again?