Question about the roof construction

Hello all,

I am trying to build my first model with the WikiHouse system. I used the size M modules for the walls/windows/doors and the size XXXS for the floor/roof. The butterfly connection of the Roof-XXXS and the Verge-XXXS do not fit together exactly at one point. Does anyone know what this could be due to? I can’t find the error somehow.
I would like to upload a screenshot, but unfortunately can not find out where.