Corners of domain distorted
 

Hi everyone, I am trying to use snappyhexmesh for a fluid domain with a large far field. Generating the blockmesh was fine but then when snappyhexmesh is generated, the corners of the domain (all 8 of them) have a distorted and almost inverted element. Ive looked through all the quality settings but nothing seems to fix it. Any ideas what causes this? Thanks