You guys need to have adhesive behind the speaker. You need enough for it to stick and not vibrate. Either use Tesa 61395 or PET heat resistant red double sided tape.
Also when the phone gets damaged more after opening that is the technician's fault.
Because I have done so many HTC One M8 screen replacements. Replaced the camera on the same M7 5 times stripping it apart without damaging it. I also do charger port replacements on them.
Honestly I don't like doing HTC One M7 screen replacements. M9 especially NO.