Deeps gullies on the tracks, filled with loose rocks, where the rain has washed away the sand/soil.
I thought you were saying they'd added rock gardens where dirt has even eroded but now I see I may have misunderstood...
Great thread for non-downhillers too (as in I don't race or own a DH bike though I do enjoy uplift days!) When I'm riding at my best I do fewer of the listed things wrong but I'm always held back by fear of disaster. After a couple of days of welsh uplift I noticed I was riding all the open fast jumpy local bits quicker, like my acceptance of what speed is safe had been recalibrated. The key thing was that my ability to squash kickers on the trail had got better, both handling the forces and keeping the bike balanced, so I was in control.
I'm not fast now but I'd be so slow if I hadn't been chasing faster riders for the past few years. I cannot conceive how quick a pro downhiller must look in real life!