If you have cue notes on a stave, if there are clef changes or octava (8va) lines present in the cue, they will appear and the stave will not be hidden. Even if show cues is unchecked (for a full score).
The strange thing is, the 8va lines will be visible, and the clefs - but nothing else. The trouble is that the hide empty staves algorithm will not hide those staves - even though they technically are empty - because of the items still showing.
My apologies if this has already been reported. I do not remember this in 3.0.1.
WIndows 10 Ultimate
32 GB Ram