I wanted to highlight issue that was already reported 3 years ago here: T175723

Originally reported by Moonny, Geez year ago wrote "All of the issues have been confirmed and scheduled for a fix with exception of nr. 4", but it's still not fixed.

1. Occlusion by Terrain Issues:
Problem: Objects are not correctly occluded by terrain when the camera is facing specific angles.
Details: When the camera rotation falls between 135 and 315 degrees, objects are not being properly culled by the terrain, leading to performance issues.
Video Demonstration

2. Missing Occluders for Spawned Items and Occasional Occlusion Issues:
Problem 1: Manually spawned items lack occluders.
Details 1: Manually spawned objects lack occluders, while "baked-in map" (static) objects have occluders, which leads to performance issues in custom-made locations.
Problem 2: Occasionally, occluders fail to hide models that are clearly behind them.
Details 2: Certain camera angles prevent occlusion culling from functioning correctly.
Video Demonstration (both issues are captured)

3. Proxy Occluder Inconsistencies:
Problem: Proxy occluders for map objects are not working as intended. Additionally, the behavior of proxy occluders for manually spawned objects is contrary to expectations.
Details: Proxy occluders for map objects are not performing their occlusion duties as intended. The occlusion order for spawned objects is incorrect, with the main model being occluded first, followed by proxies in proxy occluders, and other proxies being occluded last, leading to performance issues.
Video Demonstration

4. Frustum Culling Disables Shadows:
Problem: Frustum culling is preventing shadows from rendering.
Details: While occlusion culling still renders shadows (even at lower resolutions), frustum culling entirely disables the rendering of models and their associated shadows. This leads to flickering shadows when within the shadow of the affected model.
Video Demonstration

Regarding step first, I tested this running 1.29 Buldozer on DayZDiag via TerrainBuilder on a custom map and the issue still persists, please note that I rotate camera a tiny bit which causes huge difference in terms of culled objects. This is really noticeable when playing for example on Livonia, where there is less big hills, more dense forests and performance drops when you change your camera angle.

1. Objects are hidden by terrain:

2. After tiny rotation (at the edge of working occluder zone) it stops working:

   

   
   

Occluding of objects by terrain should not be tied to specific degree, it should work on all angles.