don't have time to go into detail, sorry
but check again ... it the Album Artist Field you need to check again -- if you are using the Album Artist (Auto) function this can happen. You can have multiple artists per track (using the semi-colon), but the album artist (or album artist field (auto)
has to be the same for all of them. There is a detailed article on how the auto function works. Don't clear your library; its a tagging issue or there is something else wrong.
@Mods For info this is the most asked about "issue" on the forum the last couple of weeks, imo. A sticky with a link to the article possible?