Yes, those two problems are related. If I'm correct like the normal Z3 model, the top speaker basically sits on top of the logic board on a hole at the top behind the screen. Once the screen pushes up, the top speaker will push up as well causing the contact between the gold connector prongs on the speaker to be not contacting properly to the logic board.
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It's best to buy new adhesive that is suited for the screen to replace the existing one.
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Here are some front display screen adhesives you can buy for example. These are usually applied on the front display frame of the phone first then peeled off and put screen on top.
Yes, those two problems are related. If I'm correct like the normal Z3 model, the top speaker basically sits on top of the logic board on a hole at the top behind the screen. Once the screen pushes up, the top speaker will push up as well causing the contact between the gold connector prongs on the speaker to be not contacting properly to the logic board.