https://musicbrainz.org/edit/153270885 has a single release title simultaneously in IT & EN change capitalization: from all IT (= faulty EN) to all EN (= faulty IT):
“Del suono come perla: 17TH-century italian music for theorbo”
↓
“Del Suono Come Perla: 17TH-Century Italian Music for Theorbo”
Maybe the all IT was from that language coming first in line, and maybe the all EN is from that language having more characters here, who knows?
(In Sweden, one would normally have both retain their vernacular:
Om ljudet som en pärla: 17th-Century Italian Music for Theorbo”)

https://musicbrainz.org/doc/Style#Language-specific_guidelines : has link to the Wikipedia article only.
https://musicbrainz.org/doc/Style/Language/Transliterations : not applicable here.
https://musicbrainz.org/doc/Style/Language/English : only has a special note on Japanese releases: “For releases by Japanese artists that contain track names in English, follow the indications on the Japanese guidelines.”, but checking
https://musicbrainz.org/doc/Style/Language/Japanese one finds it being an exceptional case of artist intent unsuitable for SG general advice on combining ≥2 languages with ≥1 clash of present/missing/exceptional SG.
https://musicbrainz.org/doc/Style/Language/Italian : has nothing more on point.

SG should have a general addition here, either
a) retain vernacular
b) first in line has it
c) lengthiest in line takes lead
d) or?