Neither Wakeup Nor Sound For Notifications With Custom Sound

Apr 6, 2018
I'm using Mi5S 64Gb with ROM installed (MIUI9.6 v8.3.29).
When I set custom sound for WhatsApp's or Telegram's notification, the sound for that notifications stop to play. And screen does now wakes up when such notifications arrives. Does not matter the the sound is located - it would not be played. Any of system built-in sounds work fine, but them are terrible.
The worst is the fact, that custom sounds for mobile calls, SMS and calendar are played correctly.
There are several threads on for that issue, it has not been fixed for year!
Who knows how to fix it, if possible?

P.S. Tried to root the device and replace system sounds, but failed - was unable to rewrite system audio files.