I have a piece with 4 horn parts which I have condensed as Hn. 1 &2 on one staff and Hn. 3 & 4 on the next. But when I need to change them to 4 separate staves a strange thing happens: I ‘uncondense’ Hn. 1 & 2, which works fine, but, when I ‘uncondense’ Hn. 3 & 4, Hn. 1 & 2 get condensed again. If I go back and try to ‘uncondense’ Hn. 1 & 2, then Hn. 3 & 4 get condensed.
There can only be one Condensing Change at any rhythmic position. Is it possible that you’re adding a Condensing Change for Horns 1+2, then trying to add a separate Condensing Change for Horns 3+4? If so, don’t; add a single Condensing Change that has things ticked for both pairs of Horns.
(Apologies if I’m nowhere near - this is pretty hard to diagnose without a screenshot, let alone a project.)