You guys are right, I always knew it was a previous grit issue.
With clear I can see and know how many strokes it takes to move onto the next grit. I wasn't able to dial in that process with single stage. I think the black sludge was laying into the scratch and hiding it.
Once done it was a great product. I just don't want that much excercise. If I was shooting a nice street paint job with a DA style cut and buff then I'd use it in a second. I'll still use it on motorcycle stuff but not on a resto unless I clear it.