I replace the structure files for "igloo/top" with a new structure. After messing around a bit I deleted the folder called region in my save file, to delete all existing chunks. Then, after reentering the world and loading a naurally generated igloo, the game crashed. The crash report can be found as an attachment. This does not happen, when the structure is spawned in with structure blocks. I guess that POI stands for villager point of intrests. So I deleted region and poi this time. This seemed to fix it. The structure I was loading in contained blocks which are villager point of interestes.