Percussion part problem

Currently I am preparing orchestral parts and I started to prepare percussion parts.
I don’t need second staff in campanelli so I want to remove it, but something happened with all my staffs, like „instrument change” option doesn’t work correct anymore. See the example:

Before remove second staff in campanelli part:

Why all my instrument changes are wrong now?

It looks like a limitation of how instrument changes work, I think. What you could do is go into Setup mode and change the “campanelli” instrument to an instrument that only has one stave (glockenspiel, for example). Then rename it as campanelli.

Thank you, pianoleo.

PS For some reason my second attachment is unavaible, so I am sending it once again.
This is “after”.

Yep, I found exactly the same thing as you’ve now shown in your second screenshot. The idea I suggested worked for me, so hopefully it’ll work for you too.