Hey g4tobauer,
Thanks for report! I was able to reproduce this in 4.9.2, 4.10.1, as well as our internal builds, and I’ve created a bug report for issue (UE-24850). I’ll post here when I see any update in it.
Until it’s fixed, this can be worked around by setting Rotation to 0,0,0 in Details tab. Once these have been zeroed out, and Use Pawn Control Rotation is disabled, you should be able to rotate component again.