This message is spammed hundreds of times before a server crashes:
[Server thread/ERROR] [net.minecraft.world.gen.feature.structure.Structures/]: Unknown structure piece id: valhelsia_structures:small_dungeon

I assume it's an unknown structure piece id. This occurs in the ocean.

Is there any update on this? I'm getting the same error and crash, but I want to make sure I have the right culprit. Thank you.

I think I may have fixed it for the 1.14.4 version, and it should be fixed in the next 1.15.2 version as well when that gets released.

I'm also getting that error message. For me, the server stops working as soon as the server tries to load the structure. I'm using v15.0.2

Edit: @Vaelzan Can I disable the mod temporarily without breaking the server or any blocks?