[Redmi K20 Pro / Xiaomi Mi 9T Pro ROMs, Kernels, Re] Peter the Great:
I had the same problem as you! I was actually going insane, I even did a clean flash and the problem persisted! I ended up soft bricking my phone and went back to MIUI, which didn't have the problem, I went back to EvoX and the problem persisted! So what I did was went back to MIUI, then I flashed the 5.9 version of EvoX (not the "ota" update, the one right before it on SourceForge), and while I set it up, this time when restoring my backup from Google, I checked everything EXCEPT system settings. This somehow didn't bring the problem back, and now I just recently finished setting up all my 150 apps again lol, but no more audio issues. I'm not updating my ROM until a new update is released.

I have a new problem though, TWRP is not persisting, meaning when I boot to recovery, it goes to fastboot instead. I tried flashing dm-verity or whatever, but it still doesn't persist.

I also have another new problem, whenever I go to fastboot mode, I believe it resets my "misc" partition, which apparently tells your phone how to boot, and so I can't leave fastboot mode by holding the power button (it'll just go back to fastboot mode), and instead I have to go to a PC and type

fastboot continue

to get back to the ROM. That doesn't solve the issue though, since the misc partition is still "bad", and so if I reboot system from the ROM, it'll take me to fastboot mode again. So what I needed to do was boot to to TWRP, using

fastboot boot twrp.img

(locate your TWRP recovery image file), and then using adb commands, I located the misc partition using

adb shell 'ls -d $(find /dev/block -name by-name)/*'

(find the line with "/misc" at the end), then backed up the misc partition using

adb pull /dev/block/platform/soc/1d84000.ufshc/by-name/misc misc.img

this will create a misc.img file in your command line location, which can be restored using:

adb push misc.img /dev/block/platform/soc/1d84000.ufshc/by-name/misc

I then wiped the misc partition using

adb shell 'dd if=/dev/zero of=/dev/block/platform/soc/1d84000.ufshc/by-name/misc'

and rebooted to system from TWRP, and it booted properly into the ROM! I then rebooted to system from the ROM to test, and it did indeed boot back to the ROM. So what's the problem you may ask? Well, if I ever decide to go back to fastboot mode, I think it resets the misc partition, because I can't go back to the ROM again, instead taking me back to fastboot mode, and if I use

fastboot continue

it'll boot to the ROM but as before, rebooting to system will take me to fastboot instead, so I have to wipe the misc partition every time I go to fastboot (which requires me to go to TWRP anyways, which I also can't boot into without a computer since it won't persist).

Hopefully someone has the answer to these two problems, and hopefully I solved your audio problem, as it was driving me insane and also uses TONS of battery life too! It makes your cores go to max frequency briefly every 7 or so seconds, I looked up the logs and about 5 other people in the whole world have the problem, no solutions though. I thought it was due to me flashing that viper zip that someone sent in this thread a few pages ago, but it actually did work, this audio issue started happening randomly, and I'm so glad someone else has the problem (sadly) so it can't just be me.