Yeah I understand, will try to match all the debug requirements next time but as I am using almost only the Live TV in LE, it's hard to provide you with the 'corrupted' files. I know it's hard do debug if you can't reproduce it. But now it's really easy to crash Kodi when the TV signal is weak. Never seen it in past. The question is how sensitive it is over the corrupted multimedia files...
Thanks for your hard work.
Thanks for the feedback.
I have put the Kodi crash log in another issue report with no reaction ( LE 10 Nightly unstable / Kodi crashing on RPi 4B ).
This time the kernel panic stopped my debug activity. 
But I suppose many Kodi crash logs are still there so I could publish them (couple days later as I am leaving for holidays today) if there's a chance anyone will have a look on it.
In fact the LE stability is worse than earlier in LE Nightly builds for RPi 4B. In past, Kodi never crashed completely when the Live TV stream was temporarily corrupted.
Regarding to OOM killer - in past when it happened sometimes (usually when the Timeshift operations was requested) the Kodi usually restarted and worked for another long period. These days I saw the situation that Kodi was not able to start again. Looks as a memory leak or something like that.
I am afraid this kernel has more issues than the bug with 2 displays and perhaps should be reverted to earlier version.
I have experienced Kodi crashes and in the end kernel panic due to exhausted memory.
Connect to your RPi 4B with SSH console and copy / paste these commands there:
#
rpi-eeprom-update > /tmp/temp.txt
echo >> /tmp/temp.txt
vcgencmd bootloader_version >> /tmp/temp.txt
echo >> /tmp/temp.txt
vcgencmd bootloader_config >> /tmp/temp.txt
echo >> /tmp/temp.txt
lsusb >> /tmp/temp.txt
echo >> /tmp/temp.txt
uname -a >> /tmp/temp.txt
echo >> /tmp/temp.txt
#Then disconnect the HDD, connect it again, copy / paste these commands as well:
Then share the HTTP link from paste here.
...new kernel hangs during boot if two HDMI devices are connected (checked that here with two monitors).
Yes that was my case as well ( 2 FullHD displays attached, Secondary disconnected from power).
As soon as I started RPi OS (with earlier kernel), terminal window (that I needed for analyzing the issue) opened on Secondary (unpowered) display and the most easy way to get everything displayed on Primary display was to disconnect the HDMI cable from Secondary display and reboot RPi.
So my assumption that restoring the distroconfig. txt to earlier form did fix the issue was wrong...
Thanks for the explanation of the issue root.
Fixed by restoring distroconfig.txt from backup.
For those who fell into the same trouble, it should look like:
# SPDX-License-Identifier: GPL-2.0-or-later
# Copyright (C) 2019-present Team LibreELEC (https://libreelec.tv)
# WARNING: DO NOT EDIT THIS FILE - IT WILL BE OVERWRITTEN WHEN UPGRADING!
dtoverlay=vc4-kms-v3d,cma-512
dtoverlay=rpivid-v4l2
disable_overscan=1
disable_fw_kms_setup=1As I had to turn off / on the hanged RPi, after LE recovery I found this message in kernel log (dmesg) :
FAT-fs ( sda11 ) Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
So another necessary task was to Remove dirty bit using:
fsck.vfat /dev/sda11
Edit - see the post #8
I have upgraded from LE 10 Nightly 20210717 to latest 20210720 but it does not boot on my RPi 4B / 2GB from HDD connected through USB/SATA adapter anymore. 
There is a multiboot (RPi Noobs, menu starts without issue and when I select RPi OS it starts OK).
Boot to LE ends with a black screen and it's not even visible on network anymore.
I'll try to investigate from RPi OS what happened with LE filesystem and if it's possible to recover it somehow.
It looks several latest LE 10 Nightly builds are extremely unstable on RPi 4B - Kodi is crashing as soon as the Live TV signal is weak. Then LE starts in safe mode.
Please note the LibreELEC is a custom OS build which is lightened and tuned for multimedia. So many commands from a 'full' RPi OS won't work as they are missing.
I have no experience with Docker but perhaps you could build the rpi-minecraft container under standard - 'full' - RPi OS and then run it from LibreELEC's Docker.
It's strange. I am running the LE 10 Nightly (currently 20210703) on RPi 4B, using output GPIOs 4, 6 and 27 for relays and LED, also in BCM mode and did not encounter any issue so far.
There's a difference between GPIO pins so it may play a role... For instance, GPIO 13 supports hardware PWM while GPIO 4 does not.
Maybe it depends on which GPIO pins are you using. For instance, some GPIOs does not keep their state during reboot.
I am running the LE 10 Nightly (currently 20210703) on RPi 4B, using GPIOs 4, 6 and 27 for relays and LED and did not encounter any issue so far.
Perhaps the solution is described here: [SOLVED] AutoMounting of Partition Filesystems
so people will stop giving stupid replies.
A stupid question ---> stupid reply... Sorry... 
Google is your friend: Four Ways to get Instant Access to a Terminal in Linux
To make sure the file is executable, run the command: chmod +x LibreELEC.USB-SD.Creator.Linux-64bit.bin
It's possible your SD card is bad and turned out to 'read-only mode'.
If possible, test it under Windows machine with SD card reader, use DISKPART in command line ( How to use DiskPart to clean and format drive not working on Windows 10 | Windows Central ), reformat it with single NTFS partition and copy some files there. Then eject the SD card safely and put it again to test if it's working (the new files are still there) or not.
You may also use an USB key to install and run LE on RPi 4B instead of SD card.
I can't test on LE 9.2.6 anymore as I am running LE 10 Nightly for a long time but I did not have any Audio issues on official LE 9.2.6 build for RPi 4B in past. And the error messages from aplay are strange. The piano2.wav plays without issue on my LE 10 and this is what you should see (and hear the melody of course):
# aplay piano2.wav
Playing WAVE 'piano2.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo
So it looks to me that your LE installation is still corrupted - it might be due to improper / unofficial installation image used or an issue with your SD card etc... Use only official builds from here: Raspberry Pi 4 – LibreELEC or a latest LE 10 Nightly build from here: LibreELEC-RPi4.arm-10.0-nightly-20210604-f6b7711.img.gz
You may also try to install LE to USB key instead of SD card to eliminate possible incompatibility (it may also depend on the bootloader version you are running - see here for details: RE: Boot from SSD instructions )
So what's the result of aplay the .wav file now?
It looks you screwed up the LE installation with some bad plugin / Add-on installed.
Try to install the LE from scratch without any suspicious plugins / Add-ons and the Audio should work properly.
