1) artist has both music files and
2) artist has music video(s)
3) music video has the "Artist:" field populated with a LIST of semi-colon separated artists (see screenshot)
If the artist is not the first artist in the music video artist list the following occurs:
1) A duplicate entry for the artist occurs on artist page. (see screenshot) Both entries metadata are identical.
2) Neither artist page entry has a music video button (see screenshot)
This is NOT an issue if the artist is the first artist in the music video artist list. Rearranging the music video artist list so that the artist is FIRST in list resolved this issue.