Hi! Is this copyright free?

Greetings I'm interested in using this track from William Boyce's "Symphony 1 in B Flat Major" for a short film that I want to upload on my Youtube channel, as well as to submit to a few film festivals. https://musopen.org/music/30649-symphony-no1-in-b-flat-major/#recordings The link here on MUSOPEN indicates it's both copyright-free and part of the public domain. However, I did a test uploading with a random video on Youtube to test it, and I immediately got a notification that the song can't be monetised because it's copyrighted by: Entertainment One U.S., LP. Vanguard Classics. Author: I Solisti Di Zagreb. I want to know if this specific track of yours is truly copyrighted so that I may not use it (and so you are notified of it); or if it's a mistake from Youtube and it would be safe from me to use on a film festival. Thank you very much Francisco