Is it normal for me to buy a Hengba house with air leakage on the blowhole side?

The horizontal blowing of Bawu is made by the vibration of the reed in the mouthpiece. When playing Bawu, you should "wrap" Bawu's mouthpiece with your upper and lower lips to prevent the breath from overflowing from the corners of your mouth.

What you said about "air leakage on one side of the blowhole in the eighth five-year plan" may be because the blowhole is not tightly wrapped with lips. If not, it may be that there is no glue between the blowing nozzle and the bamboo tube in the eighth five-year plan, and there is air leakage. If so, the repair is also very simple: carefully drip the gap with 502 glue in the leaking place, and then hit it when it is dry.