Could you perhaps try if adding
bra,pob/pb as "Default subtitle language" makes a difference?
(under: rightclick > Options > Preferences > Subtitles [Subtitle properties])
N.B.:
At this option at the bottom of the "middle column" type
bra,pob/pb,por directly into the writable box.
I don't know if it may work, but I don't know the exact differences between Brazilian Portuguese and European Portuguese either, so I'm unable to really test.