"artifacts / lines" on my world map (depending on screen size?)


Im having those artifacts on my map and I dont know what I see there, where its comming from and how I could fix it.
The map is created with 100k ISM cubes.

First I thought I might have issues with the ISM “dirty render state” or some forloops missing/skipping lines. But then I noticed the existence, amount and position of those lines is affected by the screen size and camera position/update. For example when I eject and change the camera a little tiny bit the artifacts are gone.
Here a gif of the editor where I change the size:

Anyone knows what this is about?