In my project I created a spline-based PCG using data assets, because the scene consists of a number of islands, some close to each other, some further away from any other. I instantiated this PCG a number of times, covering either a single (small) island, or some adjacent islands together… (I could use a PCG volume but I wanted to have control over the settings per instance).
All objects spawned in the PCG have nanite enabled.
Now, when I move the cursor over the project, it can happen that the image on screen suddenly blurs and is filled with large planes, all details are gone.
It seems to happen if the content of the viewport changes fast when moving the cursor but also when I run a cinematic sequence and the scene changes fast, but I got it too when trying to move an object slowly.
I can save everything, and after reopening the viewport returns to normal.
UPDATE
As it turns out, the cause seems to be related to loaded and shown spline-based PCG’s. If I hide all of them, can do everything, also when I clear them. If I enable just a number of them, it seems to be fine too.