I have a texture pack on. FYI this issue also only appeared after I deleted chunks using Amulet Editor (deleted overworld chunks but not nether chunks), tho I'm not sure how that could make this happen. This is the link to the copy of the world I discovered the glitch in:
I deleted the chunks of the nether portal in the nether then rebuilt it. It still brought me back to the same position in the overworld without a portal. I'm sorry, is this what you meant?