The downward transition from canter to trot at X while crossing the diagonal is an excellent example. This movement first appears in Training Level at test 3. The movement is done on a left lead canter. In First Level, it shows up at test one and two, also on the left lead.
I have been schooling Speedy like crazy on the canter to trot. He can pick up the new lead just fine, but getting a nice downward transition while crossing the diagonal has been frustrating. He can do the transition quite well on a circle, and he can do it moderately well down the long side, but when sees the diagonal, he wants to lengthen instead of staying more collected. After working on it for a solid week, at least I know why and have been able to work on a fix.
The main problem is that Speedy is heavy on my outside rein. It doesn't matter which way I school it, left to right or right to left - he still wants to run through my outside reins as we cross the diagonal. Since he is so heavy on his forehand, he can't come back to the trot without hollowing his back and jerking his head up.
I've discovered a few things that help. As I go into the corner, I have to give a really good half halt and pay close attention to the bend. If I let him get too straight as we cross the diagonal, he gets heavy. If I keep a bit of a bend, I can keep him more firmly on the outside rein.
The other thing that is helping is that instead of using the whole length of the arena, I am doing 15-meter canter circles with a downward transition just as I leave the circle. Then we pick up the new lead into another 15-meter canter circle. In all, we make a traditional figure eight that looks like two tear drops joined at the points.
On the days that he gets it really right, I can feel the flying changes just bursting to come out. I need him to be patient though as he needs to improve his trot to canter on the long diagonal first, which is really about taking more weight on his hind end. I don't want just one flying change, I'm going to want a whole string of them!