During the course of a CPU render, black pixels will be applied to the render in a seemingly random pattern.
CPU render with i7-8700B and macOS 10.14.5 Public Beta 2 to 500 iterations. This issue occurred without the Public Beta as well. GPU renders of course work just fine. This scene is alas too large to attach, but any scene will manifest them after awhile. They appear faster in more complex scenes.
If you look closely the same black pixels are noticeable scattered around the image to a lesser extent. This is the scene attached.
For the nissan scene, I think the black pixel are a result of rendering with both the CPU and GPU at the same time.
For the bottom image I think the noise is a result of low sampling and low light.
These are CPU only renders, as specified. These issues have unfortunately been here since RPR 2.0.32. I am aware the noise on the second is caused by low samples/light, but that's not what I am referencing. There are small, single black pixels scattered over it. These are the problem.