Spawning underground

[jjplay175]

me and my gf are playing hexxit but for some reason when ever she joins the server she is put 5-10 blocks under her position completely putting her out of sync, i can see her hitting fine ontop of land where she should be and once she gets out her person starts moving but it's out of sync and it's causing her to lag out due to that issue

Why is she spawning underground? Also the server randomly crashes when we move between areas like when a spacific dungeon is spawned so my question is, how do i preload a 10k x 10k world

[weirleader]

per this conversation, MCEdit or WorldBuilder will do the trick.

I just tried it with WorldBuilder and it was rather simple.

EDIT: Sorry, no idea about the spawning issue.