Hello, welcome to the community - we’re here to try and help 
Firstly some questions
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Are you using Look-up or Scan function in Picard (they are two different methods and can return different results)
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Have you adjusted your Preferred Release Types setting under Options at all?
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and most importantly, can you give us an example (screenshots are sometimes best, of Picard with the file that has picked up the wrong details) - you can paste directly into the reply window here without needing to upload with a third party provider
An educated guess right now would be that you’re using Scan, which uses the AcoustID community database (which works closely with Musicbrainz but is not a Metabrainz product/service). This tool that is built into Picard will effectively “listen” to your song, create a fingerprint, query AcoustID’s database and if there is a MusicBrainz link in their database, load that information into Picard.
The problem is that there are many instances when AcoustID fingerprints are incorrectly associated with MusicBrainz recording entities, causing this behaviour.
(If you’re curious as to how profound this issue is, see Report showing acoustids likely to be bad link to musicbrainz recordings )