If your hips rise faster out of the hole than your head/upper body, you're going to end up GMing it. Really focus on driving your head up/back out of the bottom of your squat. A lot of times this is a focus issue, but sometimes it can mean a weakness in your legs or your core not being strong enough to maintain the isometric contraction.
Also, when I get tired/unfocused on that last rep of the last set, invariably I end up with my knees extended at the top before I pull my back up, and I'm basically doing a GM at the end. I'm not doing enough to hurt myself yet, but I really need to work on that. Thanks for any advice y'all can give me.