Ladybug sunlight hour analysis issues

Hello,

I'm trying to make a sunlight hour analysis with Ladybug. It sort of works but I wonder why there are some dark grid units where I think there should be light ones?

The first image is of a more simple environment I made when trying to troubleshoot. The second image (original city site) is showing the shadows sort of correct in top view but shows the same strange dark grid parts in perspective view. Why?

Some help would be great! Thanks!

Maja