Also encountered this today. Would be nice with a fix but particle nodes is coming, so it will probably be fixed then...hopefully.

It worked, thanks.
I really didn't though volumes was affected by this.
A bit annoying, but i guess it's more of a overall CAD problem than blender

In T71120#801870, @Marcin Twarowski (Tvaroog) wrote:

In the example file you attached there's an obvious z-fight where faces of the cubes align.

When rendered cubes don't blend well:

However if I move one cube slightly in x and y axis, so that z-fight is gone:

volumes blend quite well:

Windows-10-10.0.16299 64 Bits
GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.86
2.81 (sub 16), branch: master, commit date: 2019-10-27 13:40, hash: rB9b6aa740be31

Not even completely sure if it's a bug at all, but it's a bit anoying.
I bet for now i have to combine the two shaders into one cube. But my way would be quicker if it worked.

Yes the problem is still there after factory reset.

I don't get any progress until i press subdivide