Brackets don't work with 'hide empty staves'
If you bracket a group of staves (eg attachement 1.pdf), and one of them subsequently becomes hidden on a later page, the remaining one does not have a braket (2.pdf). If you try to add a braket to the unhidden staff, it is misplaced and you get two brackets on the system with unhidden staffs (3.pdf)
Comments
It would in many contexts be correct to not show a bracket for a single staff, so it's not a bug per se -it's oftewn expected behavior. But indeed, not always. Ideally there should be a way to control on a per-bracket or perhaps per-staff basis how it responds to "Hide empty staves". See also #108066: Increased Bracket Functionality.
As for the second point, in order to investigate it would help to see the actual score and precise steps to reproduce the problem.
In reply to It would in many contexts be by Marc Sabatella
Well in an orchestral score for example if a single instrument from a whole group is all that is visible, it still gets a bracket, the point of the brackets is to bracket groups of instruments. I have just had a look at a few random scores (in digital and physical form) (not the most scientific method I grant) and none of them have brackets dissapear system to system like this. Also, keeping brackets visible on a single visible staff is the default behaviour in Sibelius.
From what I read in your link from what I understand, they want the opposite. So there really should be some level of system by system bracket control.
Regarding the second point, the point was I tried to 'correct' by adding a bracket in the second system where it is missing, to staff 1A. Musescore puts the bracket and notice it is offset to the left, presumably because the original bracket is there but invisible. I attached the score anyway.
In reply to Well in an orchestral score by JFrost
FWIW, there are contexts other than orchestra scores to consider. In lead sheets that go back and forth between two staves and one total (not part of a larger score) it would be more common to not show the bracket on the systems of only one staff.
Anyhow, I have opened your score, what do I now need to do to see the problem? I don't see anything wrong offhand with staff 1A - it is grouped to 1B and 2A as I assume you intended.