I experience the following problem in Dorico 5.1.21.2098 (Windows 10).
When I open Layout Options > Staves and Systems > Staff Labels, I see this:
I check the box next to player 10. Apply. Close.
I open the Layout Options again, immediately. I see now this:
Issue: the scrolling window to the right, to select/deselect players, does not have the same height anymore, and you don’t see the vertical scroll bar anymore, making it very difficult to scroll through the players list.
Current workaround: save the project, close it, and reopen it.
Any suggestions?
Suggestion for improvement: it would be easy to have a button to select all players at once, and to unselect them all.