Fixing your light-seat or jump position is easy 9/10. So here are my go-to's and quick fixes that help most jump position/light-seat problems.

1. Shorten your stirrups, and then shorten them again. SHORTER!! When I jump, I shorten my stirrups so that my knee is bent to a 90 degree angle. My thigh is at a right angle to my lower leg.

2. Heels down. Press forward and down with your heels to stop your leg sliding back over fences. If your leg slides back, you'll be less secure and might struggle to keep your hands independent. So heels DOWN.

3. Push your seat back towards the cantle - usually this happens quite naturally, the horse's movement normally does it for you. If your seat normally ends up over the pommel when you're in mid-air, you need to push your seat back.

4. Get out of your own way. If you keep your hands at the base of the horse's neck, they will end up in your way and you won't be able to fold properly. Think about pushing your hand towards the horse's ears a little bit, so they don't get stuck in your stomach.

5. LOOK UP, with soft eyes. Breathe, and allow your vision to include what's happening to either side of you. If you can only see a 1m square section of the wall in-front of you, you're too focussed, and tense.

"I'm a classically trained rider/trainer, who teaches all disciplines including Franklin balls & positional work, in-hand work & long-reining, equitation theory, and stable management. I offer goal-focussed coaching, to all levels of rider including first-time horse owners and riders with disabilities. I hold a BSc Equestrian Sports Science, BHS qualifications, Franklin Ball certified trainer, and NLP Practitioner".

Pivo meet is a great option for live remote coaching. You don't need someone to video, just your pivo, phone, and some bluetooth headphones.
In-hand & long-reining; dressage & flatwork; positional correction and/or Franklin ball lessons are all available.
https://uk.pivoriders.com/?frmrd=y

The other option is Wise Owl Equitation; an online platform designed specifically for remote coaching of riders & equestrians, allowing me to teach riders anywhere in the world. Dressage/flatwork, in-hand work, long-reining, Franklin balls & positional work, equitation theory, and stable management lessons are all available.
I've kept my prices affordable, so everyone can get involved;
I charge just £20 for a 60 minute, 1:1 lesson and only £10 for a 30 minute slot.
I charge £20 for video commentary (video analysis). Via the platform.

Click for my Wise Owl Equitation profile

I use these exercise a lot, they are an absolute staple, both when producing horses and coaching riders of virtually all levels.

1. Clockface
4 poles positioned at '12', '3', '6', and '9' on a 20m circle or slightly larger if your arena allows. It's very simple, you ride around the circle over the middle of the poles, generally in trot or canter. It's great for testing how regular and consistent your horse's paces are and working to improve the regularity of paces, it tests how accurate you are as a rider and makes you really think about control, it encourages horses to settle because it's very predictable, and the poles help to create more hind-end engagement whilst inside bend is maitained on the circle. More advanced horses and riders can raise the poles slightly, and advanced combinations can replace the poles with fences (but don't go too mad with the height, steering is required for this exercise!).