Murphy’s Law that I can’t replicate it again now - which is why I said I wasn’t certain about the cause of this. Now it’s behaving again as it was originally, without issue.
I certainly don’t mean to waste your time so I’ll keep monitoring it to see if it occurs again.
To answer your question though, it appeared to be connected to the AAC ‘format’ and not necessarily an AAC file. As long as the AAC option was at the top of the list as the last used option, it crashed out as soon as I tried to select a recent folder. If I changed the last used option to AIF and then selected the folder, there was no problem. That’s why I thought it was linked to the AAC format somehow.
But with it behaving again, I’m willing to concede that it could be on my system. I’m just sure what could have caused it because the workflow procedure didn’t change and nothing was added or removed throughout.
I’ll keep an eye on it and post again if I run into the same problem. Thank you for responding.