With CircleDOF enabled artifacts will occur when getting close to a translucent plane with an object behind it. This does not occur with any other DOF method or if "Render After DOF" is disabled in the translucent material.
Found in 4.20 CL# 4369336, 4.21 CL# 4613538, 4.22 CL# 4666322
The object behind the plane will appear to be sticking through as if it was clipping through.
The artifacts would not appear.
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-67784 in the post.