Hello!
I had the same problem as you. I also thought i had a problem with my mic. And before i tried the XDA trick I flashed a file called "
fw_beryllium_miui_POCOF1Global_V10.0.6.0.OEJMIFH_c5f0857b02_8.1.zip". I think that when i flashed that zip it replaced the modem file and the problems...