Musescore 4 ossia

I've created a score with an additional stave for the purpose of adding an ossia for the final bar of my piece.

I've followed the guidance and used "format > style > hide empty staves within systems", and have hidden the individual bars on the last line of the piece.

It has all worked fine, except on the first line of the score, where the additional/ossia stave remains. If I individually hide these bars, it leaves blank space where I don't want it. I think it might be because of the anacrusis at the start of the piece - but literally the only bar of the new/ossia stave I've edited is the final bar.

Any ideas? Is this a bug?