Can you show a video or couple of images demonstrating your setup for your scene? Or if you have a sample scene setup I could take a look and give more direct feedback.
I really would have expected HZBOcclusion enabled to help more so here, but I guess there could be some edge cases where it wouldn’t depending on how everything is set up. With doors opening, depending on how fast it opens you may want to slow down the door opening to hide this.
Another alternative would be to use the console variable for “r.AllowOcclusionQueries 0” to disable hardware (GPU) occlusion queries. This doesn’t disable frustum culling or cull distance volumes, but just dynamic occlusion that results in this popping. So what does that mean you may wonder? That means that anything in the cameras frustum direction will not be occluded. So the wall/door would not occlude anything behind it leaving it rendered ALL the time. You would need to extensively use cull distance volumes, Max/Min Draw Distance settings, and Precomputed Visibility to no longer render these when not and occluded by another actor. I recommend using other methods to hide the popping before disabling hardware occlusion queries, but it’s an option. Also, if you do use it. I would only recommend it being used when absolutely needed for the level and not as a project wide solution.