Yup, i see.
Usual suspect, has something to do with shading & normals (on long thin polys).
Just do a vertical cut through the middle (ctrl+R) and observe ;)
PS
Creating NaNs (black pixels) influences denoiser also... thus makes them bigger, more pronounced.
BTW
There's no need to model beveled edges of the screen, leave them flat (use simple plane/4 vertices).
Edges on real products are usually hidden behind the frame ;)