Riding a horse that chips in before a jump is not enjoyable for anyone. Of course, it can happen to anyone very often if the stride which the fence was approached on was wrong, but for many horses it becomes a habit that seems like ti's impossible to break !
First of all, its important to realize what this is and why it might be happening !
You can find on this website a lot of explanation, who can help you.https://stridesforsuccess.com/reforming-a-horse-that-chips-at-the-jump/
Add more leg to the jumps like u are asking for a long spot or make the jump a hole higher if more leg doesn't work because sometimes horses get bored with small jumps if you jump smaller ones because my mare got much mor excited jumping 2'3 than 2ft