If you're seeing a Red X in the MLC column, download your Detailed Results report. If "Multiple Registrations" appears as the issue for a song, this can mean one of two things:
1. The song has more than one registration in the MLC. The songwriter running the review is not collecting publishing royalties on all of those registrations, which means some earnings may be going uncollected.
2. Recordings of the same song are matched to different registrations. This means the songwriter or musician is not collecting correctly for those specific recordings. For example, if Robert Plant is running a review and sees "Multiple Registrations" for Stairway to Heaven, it could indicate that a particular recording of that song is matched to a completely different work in the MLC; one that is not Stairway to Heaven.