The song "Sam Smith Feat. A$AP Rocky - I'm Not the Only One" (3:43 min) is found two times with manual match.
The acoustid https://acoustid.org/track/d578bd40-33a6-4137-83cb-867e240c1906 with two recordings and both have an equal no of sources, in this case you could eventually compare the title and artist (once more), or take the first one.
I deleted the second recording Tony Orlando & Dawn - Save the last dance for me, because in the part Additional user-submitted metadata of this acoustid suggested that the song "Sam Smith Feat. A$AP Rocky - I'm Not the Only One" is the right one to match.
Now that the second source is deleted the song is matched.
Currently if two recordings are linked to an Acoustid and both have the same number of sources the last one returned from Acoustid will overwrite any other recordings with the same no of sources and hence the last one added will be returned. This is incorrect but not sure we want to do the onlyUseRecordingWithMostSources option is enabled to prevent bad Acoustid links but if two recordings have the same no of sources so there is no clear winner can we trust either.
And really what are more concerned about is when an Acoustid links to completely different recordings, i.e different songs by either
1. same artist, in which case one is clearly wrong
2. different artist and song, may both be valid but when matchig a single song how do we know whch except for match on existing metadata, but this relies on that existing metadata being correct.
Solution as follows:
1. If multiple recordings have the same number of sources then return releases for both recordings but only if all the recording song titles have the same (lowercase)name, if they are different names very hard to know which (if either) is right so just don't return any.
2. Additionally even if onlyUseRecordingWithMostSources is disabled (as it is when matching multiple songs to a release) then instead of returning releases for all recordings linked to the acoustid we now only returns releases for the recording with the most sources AND for any other recordings that have the same name as the recording with the most sources.