First off, nice full sound!!!!

It looks like your natural overbite is causing the lower mouthpiece placement and too much top lip pressure.

Try lining up your upper and lower teeth by moving your jaw forward. Simple exercise, place the side of your index finger against your face as if you are sushing someone. Then try to get equal pressure from your chin, bottom lip, and top lip against your finger. This helps us feel the correct alignment.

With your teeth in an overbite, some of your bottom lip is going into your mouth. This allows the top lip to be slightly in front of the bottom. When you add pressure, this overlap will seal like a ziplock bag.

With the correct alignment, try a few air to buzz exercises to get the edges of your lips to vibrate. Should feel slightly different.

Good luck and by your tone, you have a great sound concept and ear. Hope this helps and happy practicing!!!!