there is an issue where if a schematic uses blocks from the double slab mod (https://www.curseforge.com/minecraft/mc-mods/double-slabs), placing the schematic will cause the entire game to crash.
as well as the preview of the structure not rendering in world.
attached is my multiMC log, with the relevant crash log being at the very bottom
https://pastebin.com/XCfi64Mw

Duplicate of #409