1. Check if you wrapped leg is parallel to the floor in the split, if the wrapped leg is perpendicular to the floor, it unravels.
2. Part of what keeps the cartwheel drop smooth is activation in the body to keep the legs/hips/torso aligned while falling. Strong activation keeps the pole from closing the angle of hips or knees until you choose. Folding at the hips and/or the belly turning towards the floor are some of the usual sticky spots for this variation.