This has happened to me a few times but its so mind boggling that I dont know what is wrong and causing this wierd recess artifact that sometimes appear on my displacement map.
I am still trying to learn to get some nice clean displacement/bump for my mesh and so far that is some improvment tho now am seeing this on the cuff.
I am not sure how to get rid of this.
Using a mia_material, displacement map, and mental ray subdivision approx, spatial if that helps.
Thank you for reading~