Specific trees at some point stop dropping shadows in the viewport

Specific trees at some point stop dropping shadows in the viewport. After I close/open project again, everything is fine for 5-10 minutes and then again, no shadows.
I was not able to identify why always the same trees, no others, all trees are naninte. I don’t have warnings about video memory or somethig else (4060ti 16gb and 128 Gb RAM).
Shadows are back if do r.RayTracing.Nanite.Mode 1, but it hits perfomance very hard.

This is not the first project with intense vegetation, before it was more trees and worse GPU and still didn’t have this problem. Everything had shadows and only fps was effected.