He'd done 12 a few times before but they'd started to quickly deteriorate. He would skip a pole here and there, usually when he was supposed to turn left, so I suspected a medical cause. I took him to the chiropractor just before my trip to Peru, who found a source of tension and pain in Cai's back.
After the trip, I was able to attend two drop-in practice sessions at Ace, and we spent all of our turns working on six poles. I found that his footwork was improving and he was learning to single-step the poles. However he was still frequently missing a middle pole. I pulled out the 2x2s and rotated the middle pair to help him out. I could see his muscle memory improving.
I didn't think he was actually ready to go back to the straight set of 12, but I tried it in class anyway. And lo and behold, after a couple of false starts due to running at the poles at speed, he did it! He got many small pieces of hamburger as a jackpot reward!