Notehead set problem

I’ve replaced noteheads with rests previously with Dorico but find it doesn’t seem to be working with Dorico 5 (I expect I am doing something stupid).
Here is an example of what is happening …

The Notehead set in the Library looks like this …

Any suggestions appreciated.

I have tested using rests for noteheads in Dorico 5 and it is working for me. Since I don’t see anything wrong with the way the quaver rest looks in your notehead set, I would need to see your project or a cut-down version of it to figure out what is going wrong.

Here’s the project from which I took the image above …
rest problem.dorico (730.9 KB)

The problem is that you have kept the noteheadBlack notehead in your Rests notehead set, and that notehead is set to be used for durations shorter than and equal to a crochet. Execute Edit>Select All and Edit>Notations>Notehead>Default Noteheads. Then execute Library>Notehead Sets, select your Rests notehead set, select the noteheadBlack notehead, remove it from the set and click OK. Now select the notehead in bar 11 you want to change to a quaver rest and execute Edit>Notations>Notehead>Rests.

Thanks very much, John.
That works perfectly though I couldn’t see how to delete the noteheadBlack notehead since the trash is greyed out. But unchecking the ‘durations shorter than’ box cured the problem.
I would quite like to get rid of that black notehead since it shows up as a red triangle alteration. How do I get rid of it?

You should not change the definition of the noteheadBlack notehead because such changes could affect other notehead sets in which noteheadBlack is used. So check the ‘durations shorter than’ box for this notehead again.

I could not remove this notehead from your Rests notehead set until I made sure that none of the noteheads in your project were using that notehead in your notehead set. That is why I told you to execute Edit>Select All and Edit>Notations>Notehead>Default Noteheads. Then I was able to remove it.

I’ve started a new project containing only minims i.e. no noteheadBlack noteheads.
I set all noteheads to default as you suggested, executed Library>Notehead Sets , selected Rests notehead set, made sure that the duration box was still selected as originally, selected the noteheadBlack notehead but the trash is still greyed out. So the quarter note remains with the same duration.

I know that if I try to create a new notehead set, the first thing that appears is a quarter notehead.

The icon you click to remove noteheadBlack from your notehead set is the second one just under the pictures of your rest noteheads. It looks like the letter U with an arrow coming out of it.

Oooh! I never knew that. I thought those signs concerned importing and exporting.
I do believe it now means that I understand what was going on.
Many, many thanks for your help, John