Polygons shaded black and some flashing black.

Hi All,

I just wanted to ask if anyone had any idea why some of my polygons flash black and others are shaded black in UE4. Only some do this.

In the case of flashing, I’ve no idea why it does this. Even without rebuilding the lighting it does this.

In the case of them being shaded, this only happens after I rebuilt the lighting. I’m not sure why this happens on some polygons of the mesh and not others.

I’m sure there’s a simple solution to this, but I can’t find many similar cases on the net, especially not in the case of flashing polygons.

If anyone can help, I’d appreciate it. Pictures are attached below.