are u goin to take it for screen replacement? have u try edl mode? but its only possible easiest from bootloader/fastboot mode, just type fastboot oem edl, then flash it with anything u wish to..
mi 5 prime, so far so good.. it works with sony smartwatch sw2 also, but added watchfaces need some reboot to be working, thanks for the effort xiaomi.eu team
mine is good enough.. try compare it with another mi 5 devices.. if it does not loud, then it must be your speaker is the problem.. take the warranty or take it to the neareat service centre for a fix