Glide kips are the most complicated basic movement in women's gymnastics. The problem you're describing could be from just one thing, like abs strength, or a number of things like.......
Extending by letting the glide's energy pull you straight instead of pushing your hips toward your toes as they (hips) begin to pass below the bar.
Forgetting/failing/ no knowing to lift your hips as a follow through to the extension so they can drop down a bit as you bring your feet to the bar, because there is sort of a down-up-down-up motion your hips travel through during the glide-bring your feet to the bar portion of a glide kip, and missing either an up motion or down motion will mess up the motion that comes next......... I'm suspecting this is the part of the glide where something's going wrong, probably from lifting your hips and holding them up too much as you (try to) bring your feet to the bar.
Letting your shoulders get stretched, at the end of the glide, beyond your ability to work with that much swing once the glide peaks and begins to move back toward the bar.
Fortunately, for you, it seems you have the hardest part of the kip already figured out and behind you. That's the part of deciding you want the skill, and are willing to do what it takes to get one.