Weird shadows on a POM material

So these weird shadows appear behind planes with textures that have alpha transparency (e.g. grates, as shown in the second screenshot), and on the edges of the screen like a vignette.

How can I fix it? I use Lumen on UE 5.7.

I’m going to guess it’s a screen space shadowing artifact. What are your shadowing methods?

If you’re talking about global illumination, then Lumen (as stated in the post). This is how it looks with screen space. It’s also very flickery