What's causing these weird black stripes?

So, I have a problem with a level I’m working on. In this level I’m using purely movable point lights to light up the level and most of my meshes feature these weird black stripes that appear and disappear depending on the angle you view them from.
Here an example:


And this is happening all over the place for some reason. At first I thought it might have been that the meshes use small lightmaps or something, but those meshes in particular have a 256x256 lightmap, which should be more than enough for such a surface, but I still get that. Does anyone know what causes that?

Thanks in advance.

I’ve seen a similar issue with terrain, and it had to do with the light direction and shadows. Does moving your light source somewhere else produce this same result?