How does this happen?

So Friday Chandler landed his tantrum, then did like 8 in a row and landed them all. Did one on Saturday in his run, then this week we go out and he has totally forgotten how to do it, although he says he is doing the same thing as he was. He is doing some kind of funky rotation and coming around sideways!I tried telling him all the things like: head straight back, square up..etc... He has tried about 5 or 6 and now feels like he has lost it. Has anyone ever had this experience of having a trick down and then not?