Ambient Occlusion Decal Disappears Depending on View Angle

I have a big problem with Ambient Occlusion Decals.
The material is setup like this.

“DBuffer Decals” are enabled in the project settings. This decal is attached to a movable actor (car) with the following settings:

ShadowDecal = NewObject(this, UDecalComponent::StaticClass());
ShadowDecal->AttachToComponent(GetOwner()->GetRootComponent(), AttachmentRules);
ShadowDecal->SetRelativeRotation(FRotator(-90.0f, 0.0f, 0.0f));

The post process volume in the level has “Ambient Occlusion Intensity” set to 1.0 (Seems like this settings affects decals along with SSAO).
The problem is that the decal sometimes visible and often not, this also depends on the view angle but somehow also the location i think. GI is completely disabled, unused or set to 0.0 on all lights. Except for the directional light no light in the level is casting shadows.
I also tried changing the decal blend mode to translucent and adjusting the texture and parameters inside the material so it works and this problem does not occur. So it definitely is related to the blend mode of the material.

The funny thing is: when I drag and drop the material into the viewport and leave it where it is this problem also does not occur.

Any help?