Hello there @Daily_Gamer_Max! Let’s try to figure this one out.
The issue you are describing is tied to the asset’s current LOD values or Nanite setup. Both techs affect the polygon count of your asset, based on the current viewing distance. The closer you get, more polygons are rendered, and the farther you get, less poly count is used.
If holes are appearing at a certain point, it means that the mesh on those trees is either not properly closed, or its poly count is reaching a level too low. Adjusting the values for either LOD or Nanite should fix the problem.
Here you will find the details for both techs, how to use them, and adjust their parameters: