Searched but couldnt find anything.

I originally found this bug on a modded instance of 19w36a while testing out stuff with the far lands. I then tried testing it on a vanilla instance to make sure it wasn't an issue with the mod and discovered that it's actually vanilla issue.

Beyond x 524288 (chunk 32768), end terrain generation seems to break, causing a perfectly flat wall of end stone where it cuts off. I've also tried teleporting around near 300000-400000 blocks from the world center to find sheer emptiness and server lag.