Collisionshape becomes spiderweb-like when the mesh is too complex

It seems like the file named HolicWallOcta with its 48725 vertices gets an incorrect collision mesh ingame (use tcg to see collision). However a slightly smaller file with 46285 vertices where I remove 1 slice of the building gets a correct collision shape ingame. I'm not even sure that the difference is based on the amount of vertices because I had about 3k duplicate vertices, the removing of which had no effect whereas adding more slices to the wall to make it complete makes it a lot more spiderwebby. Spiderweb.7z