Exporting Session not saving copies of associated files

Hello - I'm trying to export my session for archive purposes and am having trouble doing so, even though it works with some sessions.

I am working in multrack mode and when I click file > export > Session I get a dialog box that allows me to export the .sesx file along with copies of the associated media. Unfortunately when I hit "ok" nothing happens. It just returns me to the multitrack screen as if I had hit "cancel."

However, with some files this process works as it is supposed to. The only thing that differs (as far as I can tell) is the sample type. I'm using Audition 22.3.0.60 on a 2019 MacBook Pro running Big Sur and have tried reverting to older versions of Audition, but to no avail.

Any ideas what else I could try?