Hello, let me start by saying that I am not an expert O(∩_∩)O, but based on my years of learning experience:

First of all, the pronunciation keys of a sound are synchronous and cannot be sorted.

Try to change it. If it still doesn't work, find out your basic skills, pay attention to whether your mouth is correct, pull your mouth together at both ends, and don't drum your cheeks. At the same time, you must not relax your mouth strength, especially in high notes. Strengthening the practice of long notes at ordinary times is of great help to the accuracy and stability of your treble.

At the same time, I suggest you change a thicker whistle (a thicker whistle will make the blown high notes sound fuller and more harmonious). When playing high notes, the chin will be slightly closed and the pipe will be lifted, which will make you feel relaxed when playing high notes, and at the same time make the upper teeth naturally increase the intensity of biting the flute head and reduce the occurrence of sonic boom.

This is my humble opinion, I hope it will help you ~O(∩_∩)O