The ambient sounds that play when near a portal are indeed disabled by the 'Blocks' slider, but the sound of going through a portal continues to play even while all sliders except Master are disabled.
I'm having the same issue with some villagers in 1.15.1 at the moment. I think it's related to the `Dimension` nbt tag. It seems to usually be -1 for entities in the nether, but these villagers which were bred in the nether have Dimension=0, which would seem to imply that they think they're in the overworld. New villagers fresh from a spawn egg have Dimension=-1, and are able to go through the same portal as normal.
Confirmed for 1.15.1.
The ambient sounds that play when near a portal are indeed disabled by the 'Blocks' slider, but the sound of going through a portal continues to play even while all sliders except Master are disabled.
I'm having the same issue with some villagers in 1.15.1 at the moment. I think it's related to the `Dimension` nbt tag. It seems to usually be -1 for entities in the nether, but these villagers which were bred in the nether have Dimension=0, which would seem to imply that they think they're in the overworld. New villagers fresh from a spawn egg have Dimension=-1, and are able to go through the same portal as normal.