Is there anything you can do to fix this? Yes, you and the rider can do alot to correct this issue, and just as already stated, you should start venturing into the world of Dressage.
How much dressage do you do with your horse? Dressage is very important to have under your belt when you are jumping, so that you and your horse will understand balance, will understand establishing a controlled rhythm. Dressage will help you to learn how to keep your horse light on her forehand and keeping your horse up and under you - so that when you are jumping, you can apply what you learn through Dressage, into your jumping.
If Grand Prix Riders spend up to 5 days a week doing dressage, there's a reason behind it - because Jumping is dressage with speed bumps. You cannot be going around with your horse flat, heavy on the forehand and unresponsive to your aids, and you cannot go around aiding your horse to be this way. You both must learn how to achieve balance, control, rhythm, engagement, lightness, response - so that you can make your jumping that much better.
Our horses reflect 100% of what we do in the saddle, so if you're heavy on the forehand, so will your horse. If you aren't using yourself properly, your horse wont be using themselves properly either.
You can do as much as you want over grids and small trot poles and small xrails, but if you as the rider doesn't understand the fundamentals of your core, seat, legs, upper body, balance, etc, etc - you wont beable to help your horse understand it either.
You can trot figure 8's till the cows come home, but if you as the rider doesn't understand how to get your horse engaged, how to contain the energy created, how to achieve and establish rhythm through your seat, core and legs, how to get your horse under you, how to get your horse light on their forehand - all that work wont accomplish anything, especially if the horse and rider are not using themselves properly.
The barn I board at is a very large Hunter/Jumper barn, who are very active in the LMHJA - none of them understand the fundamentals of dressage. None of them understand the importancies of functional and educated flat work.
They go around with their upper bodies on their horses forehands, and riding 100% with their hands and upper bodies. Their horses go around heavy on their forehands, not engaged, and flat. When their horses rush, they pull. When their horses keep rushing, they throw on gadgets, Pelhams or other stronger bits, and keep pulling.
If they stopped and took the time to educate themselves as riders on how to ride correctly using their bodies correctly - seat into legs into hands and core, core, core - they'd be better. If they took the time to establish the importancies of dressage into their horses and themsleves, they'd beable to fix the issues quicker and thoroughly, than what they are doing now.
It's sad and dissapointing. If the rider and horse are not using themselves properly, the issues wont cannot be corrected. Then they turn to gadgets and other quick fixes.