Just in-case it comes in handy for anything or anyone's interested, it seems that actually a lot of instances could contain identical terrain design (which seems obvious now you think about it) due to them being designed around each other.
This is something I've not really ever thought about a lot, or seen a lot of; during a revisit exploration of OS / RS I noticed that a large amount of terrain in the glitched areas of the instances was near identical. See below for more detail:
Some of the similarities include:
1. The slopes on the cliffs used to jump out of the area (1:23)
2. The cliffs glided off (1:39)
3. General Terrain patterns (1:55)
4. Paths (3:16)
5. Ground Patterns (4:27)
There's a lot more than these, but these are the more noticeable ones.