Can you find the track using “search”? It may just be that Roon put it in its own album? if you search for the Artist it should show all the tracks?
If you can find it you should be able to “merge” it into the album using the editor. YMMV
I tried moving the folder out of the library and then back again to see if it re-scanned it, but it didn’t solve the problem.
Then went to “storage”, deleted the folder where the album is located added the folder again, which re scanned that part of the library…and nothing.
If I move the file back to the album folder it dessappears…
I could group them toghether and get one album, but I won’t be able to sleep knowing I have a track out of the folder…sorry I’ve put a lot of effort in organizing my library.
Although I see other files have them with no issues…however when looking a the Roon screenshots in your first post the special character don’t appear to be showing, so maybe that one file is causing it issues?
Even the Tidal version does not display the special characters.
And last but thing to try might be to re-rip just that track and then place it in the albums diirectory?