Instrument change labels repeated & not registering as selections

I have a percussion part that consists of vibraphone, glockenspiel, temple blocks (on a single 5-line staff), and altar bells (unpitched percussion).

I originally worked on this piece in Dorico 2 and the instrument changes in the percussion part were very difficult to work with, since many of them happen quickly. I’m happy to say that Dorico 3 seems to have improved on those issues.

The problem I’m currently having is the repetition of the same instrument change label. It’s quite possible that, at some point, I added one as staff-attached text (because the auto-generated instrument change label wasn’t appearing). Now that they’re both appearing, I should be able to just select the unnecessary shift-x text and delete it. But instead, when I select either one of them, neither one of them registers with Dorico as a selection, prohibiting me from doing anything to them.

This happens in both Write and Engrave modes, and the layout is setup to allow instrument changes.

Try going to Engrave mode and looking in the Properties panel; you should be able, by hook or by crook, to suppress them using Properties.

Well, I hooked and I crooked and I got them looking the way I wanted them to in Engrave mode. It mostly required selecting the unwanted instrument changes and, editing their properties, removing their prefix and setting the custom text to a blank space.

I believe all of these were automatically generated instrument change labels. Is this a known issue with reduced percussion player setups, or is this common to all parts with instrument changes?

It’s common to all such parts. Dorico generates these labels automatically so you know where the new instrument appears. If you want to get rid of them all, you can disable them in Layout Options, but I’d advise against it unless you’re sure your players can read your mind and know psychically when you want them to start playing another instrument.