A few weeks ago, a member of my server contacted me about an auto-teleport bug that only occurred when the player went under y=2 (or y=3, it changes depending on your area.)
I tried this myself, and it wasn't a lie or anything. It started when I had a texture pack on, specifically the "SCP Modern Base Textures" that I had downloaded roughly a month before.
The End seems perfectly normal, other than the End Portal to The Overworld and the portal to the Outer End Islands are made of obsidian, and the smaller portals in the End Void.
However, this issue is Invalid for the bug tracker.
Unfortunately we don't accept issues related to third party Marketplace or Community content here on the bug tracker, but you may wish to contact the content creators directly. Marketplace partners have their own support channels for reporting issues affecting their content. Please visit the Marketplace FAQ section for more information, including contact links for some of the Marketplace partners.
If you can reproduce the issue in a world/realm without any third-party add-ons, please create a new bug report.
For more information, please see the Bug Tracker Guidelines.