Information

• Server version: Paper version git-Paper-188 (MC: 1.17.1) (Reproduced on Spigot as well)

• Full output of /mv version -p: https://pastebin.com/Gp3fLmYV

• Server log: https://pastebin.com/J0ggBWYA

Details

I was able to reproduce my issue on a freshly setup and up-to-date server with the latest version of Multiverse plugins with no other plugins and with no kinds of other server or client mods.

Description
My server faced an issue that the default nether (world_nether) have a massive number of chunks had been cut off. It once recreated using Multiverse Core's "mv create world_nether nether", and after several time server restarts, every "new" chunks in nether were generated differently and don't match with old ones.
However, I discovered that if I use mv create with the same seed with current (fresh, new) nether, both worlds were generated very different.
Steps to reproduce

1. With a fresh server that only has Multiverse Core plugin, start it
2. Go to nether, type "/seed" to get its seed
3. Use "mv create testnether nether -s "
4. Teleport to testnether and compare the terrain of both worlds
5. The terrain is different, how ever, the structures location is the same

Expected behavior
The terrain must be the same

Screenshots

MV doesnt dictate the actual chunk loading, so I don't see how mv will cause this. If the seed you specific in mvcreate command is correctly reflected, then nothing wrong with mv.