I'm trying to set up a private world (overworld+nether+end) but have been experiencing some weird behaviour around respawning mechanisms. Here's what I've found so far:

• In this new world (let's call it testworld), if I die in the overworld, I respawn at my bed or at world spawn (expected)
• If I enter testworld_nether and perish there, I respawn in testworld (expected), at the nether portal entrance, instead of my bed (unexpected)
• If I try this in the default worlds (world, world_nether) generated by Paper, it works as expected (dying in either world or world_nether brings me back to my bed in world).
• worlds.yml config is identical between world and testworld, and between world_nether and testworld_nether, except for the seed.

To further muddy the water, I was also playing around with keepInventory true at the same time (although the above problems occur even without keepInventory), and found these:

• In world and world_nether, setting keepInventory true in world is sufficient (dying in either world or world_nether lets me keep my items).
• In testworld, setting keepInventory true and dying in testworld (overworld), I keep my items.
• If I set keepInventory true in both testworld and testworld_nether, and die in testworld_nether, I lose my items.

I tried to replicate this in my 1.15 backup, since I recognize there may yet be some bugs from the brand new release and incompatibilities with MV4.1, but I had other troubles altogether (my inventory wasn't transferring between nether and overworld), so I suspect lack of sleep might be playing a factor and I'm missing something stupid. Could anyone lend a hand?

Server setup:

• Paper 1.16 build 24
• MV-Core, NP, Portals 4.1.0
• MV-Inventories 3.0.0
• LuckPerms 5.1.26
• WorldEdit 7.1.0
• EssentialsX 2.17.2.77

Aaaaand it turns out I forgot to set up world groups in MV-Inventories. Although that doesn't really explain how come it works in the default worlds. Closing this issue!

We're glad you figured it out (and that there's no bug lol). As for why it works with the default worlds, it's most likely because MV Inventories automatically groups them.