Portal constantly teleports you between overworld and nether

I'm not exactly sure how to explain it well in words, but I made a video showing off the bug, it has been in the game for the past few months only on servers running the snapshots. Seems to work fine in single player, but anyway, here is the video: https://youtu.be/wUBibAHv6QA

Edit: Look in the comments of the video, another guy says he has this issue too.