So, our analysis of the logs yielded a corrupt MP3, which got the number of missing tracks down to 10. Some solid detective work by @garym found the rest.
Because Roon’s importing process is based on automatic folder scanning, we need to ensure that some folders which include system files or other temporary content isn’t included. We don’t have a lot of issues with this, but the detection can sometimes go awry when bands or albums have names that match our rules. As mentioned by others, folder names that start with periods are the most common offender, such as "/...And you should know us by the trail of dead/".
In this case, a ZZ Top album was in a folder called Recycler which is another folder Roon currently skips.
@garym- you’ll need to insert at least one character at the beginning of the folder name, and rescan your storage device, then I think you should be good. Just note that ZZ Top - Recycler would work, but Recycler Album will not.
I’m also putting together a list of rules and reasons why content might not be imported into Roon, so all this troubleshooting information can be in one place. I’ll link that here once it’s published in the Knowledge Base.
Thanks all, and sorry for the trouble @garym!