That looks like your camera bounds doesn’t go to the edge of the screen, which is possible if that is necessary to achieve your pixel perfect specification.
Put another camera layered behind it set to clear all to black and make it render nothing via the culling mask.
Remember: pixel perfect can’t change a display system’s pixels if the math doesn’t come out to your spec.
Some more notes about pixel perfect stuff:
Pixel Perfect requirements are extremely stringent, like a banknote: