Terrain and location
The bad chunks, spawning near the edges of an Eden word, consitute terrain that is extremely rectangular an inprecise. This glitch is likely to be the cause of the edge of Eden or vice versa.
Theories and Ideas
-These chunks may only exist in hacked worlds. This would mean that the Edge of Eden is result of such hacking. If that is true, it can be assumed that the worlds shared as 'Edge of Eden' must have been all hacked.
-It is possible that this effect of very rectangular terrain is built up over time. (i.e. the farther you go, the bigger the rectangles get.) That would mean that terrain naturally wants to generate with bigger rectangles, but something about the previous chunk prevents it from doing so.