Great work on staying long and tight through the drop!
In the final part of the drop where the back arch can happen, your legs are passing the pole on the same side rather than pole going between the legs for the arch up. If you are able to have a sense of where you are in space while dropping, the moment to prep for this is when the back passes the pole, or if we were doing the star style rotation, where the side ways part would happen. After the back passes the pole, the legs kick on either side of the pole, kicking/pressing/arching into the back arch. Since the legs are traveling on the same side of the pole, getting the arch up is not possible.
Happy training!