Loud Speaker (Buzzer) Problem

Hello friends. My device is iPhone 6 64GB. I'm having an interesting problem. First of all, the sound started coming less than usual. I cleaned it up, but it didn't change. Then I started to open it and check it out. First of all I removed the buzzeri and reinstalled it did not change. Then I just tried plugging in the sockets, so I didn't insert the bolts. I sounded soundly. I noticed that the speaker has a bolt on the right side of the screen. The sound sounds fine when you don't wear this bolt, but the sound decreases as if it's mono. I turned it off when I said that way. The sound was again slightly reduced, and then, when I tightened the two bolts on the case, the sound went down to the same level.

As I understand it, the sound is decreasing due to pressure. This is the case when you press the right-hand side of the screen. What do you think is the defective part? I also tried it with a robust buzzer, the same. I suspect a movie with a socket on the bottom. Thank you in advance if you have experienced this before or will find a solution