Instrument picker won't open

I’m trying to change an instrument throughout a score. I go to setup, open the instrument, click the chevron, select “change instrument” and … absolutely nothing happens. What am I doing wrong?

You’re not doing anything wrong. That should work.

Ok, it was only happening on one instrument - it was working fine on the others. As a workaround I created a new instrument and copied everything from the instrument I couldn’t change into the new one, then deleted the original. That did the job, so I’m up and running again, but I was a bit nervous deleting a couple of days work (unnecessarily, I suppose, as the file was saved, but still…)

What instrument was it? Had you made changes to the defaults on that instrument?