I'm not sure if the one I faced is the same as yours but I randomly lost the sound as well. I had to reboot but it didn't happen again. Not yet at least.
I'm very new to the rooting things so your directions are a bit unhelpful since I don't know how to do those. If I can successfully get a log, I'll post it here.
I have 128 GB Mi 9. It shows as I have 100gb available. So 28 GB is system data? Isn't it too much? Am I remembering it wrong or before ROM, the available space was higher?
There is a bug when trying to set data plan on your carrier. If you touch the option, the window pops up and closes right back down. Take a note of this please.