I would suppose a bias problem. Is the scene far away from 0,0,0? Maybe you can optimize your scene coordinates. Maybe scaling the scene is a workaround.
If it is caused by the sun than it could be a workaround to use a skybox environment and disable the sun. OK, it looks not like the current setup, but it could help to finish the project.
I have seen similar effects with coincident geometry. It doesnt even have to be exactly in the same plane. If it's close this effect seems to occur at a certain distance.
I have seen similar effects with coincident geometry. It doesnt even have to be exactly in the same plane. If it's close this effect seems to occur at a certain distance.
Which is then some sort of Z fighting. That could be relatively easily solved by adjusting the geometry. The issue from Solo seems to be shadow mapping related.
How can I overcome this problem, I have tried every type of sky, clouds, no clouds, plain white HDRi, every combination of settings but still I get this:
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Is there any chance we could get at least the non-confidential part of your project file (e.g. remove the stadium if it's still under disclosure)? That'd help us a lot to fix the issue as soon as possible, as we could not reproduce the artifacts on our end yet. You can contact my directly via PM in the forums, or contact our support@enscape3d.com 
Thanks a lot in advance!
Thanks a lot for providing the model! We've just had a look at it, but unfortunately were unable to reproduce the artifacts yet. Did you try if the issue persists with the latest preview yet? Is the artifact only visible in video capturings or does it always flicker like that for you? And there's of course always the possibility that it's a graphics driver related issue, so updating those could also be worth a try 
