Reflection error with white squares appearing while moving.

Hello. For a long time (since ue4) I have a bug with the appearance of squares when trying to move.
Now I tried ue5 and tested the new map in this project, but it still stays. I tried to run it on 2 different graphic cards.

I even tried to remove all light sources and they appear even in complete darkness!
Also I checked it in NEW projects and it looks like they have it too (second video).

How can I fix that??

This looks like occlusion culling. As you pan the camera, objects that are obscured by the pillar are culled. They are brought back in once they should return to view, but it’s happening too slow and allowing the skybox to be visible.
There are a handful of ways you can help deal with this. One option is to slightly increase the bounds of the offending object, so that it can’t be culled so aggressively. Another option is to change the background to be black in scenes like this, so that when culling issues manifest they aren’t nearly as visible. I’d recommend reviewing the docs on culling to learn more.