Slashes aren't appearing in my drum set part

Hey folks, I’m trying to get rhythm slashes to appear as notes in my drum kit, but when I add stemmed slashes in the Kit Editor and try to use them they appear as regular noteheads. I can make them into slashes after the fact but I don’t want to keep doing that every time I need it. Anyone know what could be the issue?
This is Dorico Pro 4.3.30, though this file is a few years old and has been opened in the iPad version before.

I’m not sure if this will help but are you following steps 3 or 5 in this?:

Have you checked the setup of the relevant slash notehead set in Library > Notehead Sets?

If you’re not sure, the best thing to do is share the project file itself here (or a cut-down duplicate version that just contains enough instruments and bars to demonstrate the issue, if you don’t want to share the whole thing)