Artifacts such as shadow and unrendered parts of landscape when building landscape data

Hello, To be more specific about my issue I’m encountering, whether I use Displacement or not, anything I do that requires me to rebuild landscape data, after the build process I can see two types of problems.

#1 When using displacement (After building landscape data) I see small unrendered triangles In the landscape.

2# When i moved from 5.3 to 5.4 I wanted to test the build landscape data again to see if it’s fixed (without displacement) same issue just like 5.3, but since I’m not using displacement at the moment, this time I’m getting shadow artifacts. I guess it’s not the engine, is it my setup?