Just to be clear. I migrated from one Windows server to another (both my servers). I reinstalled the mods on the new server exactly and the moved the World file over. All the rest of my world appears to be there. Just not the glass walls. Is that normal? IT's not deleted, just doesn't feel like it migrated.

Well, got the same issue (Aku shima structures & items too). I'm currently trying something : I deleted all mods from my computer. Then I restarted Steam to download them. Then I upload them again to the server. I think the issue is due to the fact that mods are loaded after the saved files. They should be loaded before. Btw there's no information about how are saved native structures and those from mods. They're in the same file but some disappear. Weird.