Ambient Occulsion Deferred Decal Materials seem to ignore the Receives Decals flag that is in the Rendering section of the Details Panel for the Static Mesh.
Tested in 4.21.2 (CL - 4753647), 4.22 (CL - 5660361), 4.23 (CL - 5825806)
Expected: The cube should have no shadows on it
Result: The Cube has a panning decal rendering itself on the shadows of the cube Static Mesh
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-72653 in the post.