Bad positioning for the brown ball... too much angle... the cut had to be thin. As a result, too far down the table with the white ball for the next pot - no angle at all on the blue ball, had to play follow. The pink ball was tough, and he missed it. Ding had an even tougher position, but he made it.
The previous frame though - Ding got unbelieveably lucky at one point, crashing into pink, which hit the red ball, setting it up for an easy shot. Still, Selby has only himself to blame for the previous frames.
I'm afraid Ding can be a pushover for Trump now. He can play fantastic snooker, but he's too easy to break. I'd bet all my money on Selby against Trump, but not on Ding.