When I went to a pillager outpost to bring allays to my village I took them through the nether and when I passed the portal to go back to the overworld I saw that my allays had disappeared, I tried to recreate it and here is the video of what happened, I heard that it is a bug similar to the one in the Ender dragon portal,   that if you throw an item into the portal it appears at coordinates 0 0 but at height 300000