I can confirm that setting this to 1 fixes the issue. Tested on 2 projects in 5.6.
I’ll mark your answer as a solution for others who might encounter this issue. Thank you!
PS. I’ve discovered that you can combine both the “r.DOF.TAA.CoCBilateralFilterStrength 1” and “r.DOF.Scatter.BackgroundCompositing 1” for the sharpest edges on DoF, but the result may vary, depending on your scene.