When I place down the blocks of an end portal and turn two opposing sides inside out and I place another end portal frame in the corner of one of the inside out sides, the portal gets shifted out of its place. It might be related to this, but there are multiple ways it can happen: https://bugs.mojang.com/browse/MC-142305?jql=summary%20~%20%22end%20portal%20wrong%20place*%22%20OR%20description%20~%20%22end%20portal%20wrong%20place*%22%20ORDER%20BY%20lastViewed%20DESC