Does the crater shader have a continuity issue?
The skirt always creates a hard ring and is hard to defeat, even when it's totally smooth, it's present. At global scales, it look really bad. Here is a inverted crater to see it easier. Skirt doesn't blend right and it reminds me of surface layer blending of fuzzy zone. If you go over a certain smoothness for global scales to have a realistic huge crater, it creates a hard ring effect at the crater rim.