I put 10/20 to Near/Far clip but still goes on.. Well, i think I can live with this..
Dont know which verts are good to merge, I merge some but they turn the mesh into a complete mess. :s I'll try to make those windows by another way..
No errors.. well, this time, not even an edge showed. (config: https://i.imgur.com/ueMXofx.jpg, result: https://i.imgur.com/dxzwJcz.jpg)