Local album found in search but not listed in composer's albums

[RalphH]

This is a known issue in Roon:

Rachmaninoff album does not appear under Rachmaninoff

Had a similar problem with several classical composers who are long dead but appear both as a composer and a performer (Richard Strauss, Benjamin Britten and others). If I recall it correctly, removing ´Rachmaninov´ from all other roles than composer and primary artist, solved the issue. Reason being that roon files albums on the artist´s and composer´s page either under ´composed by´, ´main albums´ or ´appearances´, not several at the same time. So if one is both a composer and ´Soloist´, ´Pia…

The Roon algorithm cannot display an album both under composition and under performance. (I know - singer/songwriters must get a raw deal).
Looking at your tags, on symphony #2, the Artist is “Gustav Mahler” and the composer is “Gustav Mahler” which is confusing the Roon algorithm. On Symphony #1 the artist appears to be “Mahler, Gustav” which is not the same as “Gustav Mahler” and therefore does not cause confusion.
Like you I use ‘Prefer File’ import settings (including main and other performer credits). In this case I would put only the orchestra and conductor in the artist tag.

BTW - the recording of Bruno Walter conducting symphony #1 is something special.