Probably this:
Mounting system partition...
mount: mounting /dev/loop0 on /storage/.update/.tmp/mnt failed: Invalid argument
Missing kernel.img or SYSTEM!
In my case - LE is installed on internal and this image (LibreELEC-S905.arm-9.0-Leia-testing-Gendo-01-10-2017.img.gz) fails on two S905/S905X boxes...
Correct.
To have iperf(3) on a LE Kodi box,
you have to install "Network Tools" addon.
For some reason "iperf client" could not connect to my "iperf server",
and I had to run iperf3 on the server side.
These are the results of my simple test (iperf -i t300 -c <server_ip_address>
[ ID] Interval Transfer Bandwidth
[ 5] 0.00-1.00 sec 84.6 MBytes 710 Mbits/sec
[ 5] 1.00-2.00 sec 90.9 MBytes 762 Mbits/sec
[ 5] 2.00-3.00 sec 92.0 MBytes 772 Mbits/sec
[ 5] 3.00-4.00 sec 94.7 MBytes 794 Mbits/sec
[ 5] 4.00-5.00 sec 86.9 MBytes 729 Mbits/sec
[ 5] 5.00-6.00 sec 87.5 MBytes 734 Mbits/sec
[ 5] 6.00-7.00 sec 87.0 MBytes 730 Mbits/sec
[ 5] 7.00-8.00 sec 86.9 MBytes 729 Mbits/sec
[ 5] 8.00-9.00 sec 88.7 MBytes 744 Mbits/sec
[ 5] 9.00-10.00 sec 95.0 MBytes 797 Mbits/sec
[ 5] 10.00-10.03 sec 2.76 MBytes 767 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth
[ 5] 0.00-10.03 sec 0.00 Bytes 0.00 bits/sec sender
[ 5] 0.00-10.03 sec 897 MBytes 750 Mbits/sec receiver
-----------------------------------------------------------
This is on my cheap "karate" S905 box with Gigabit interface...
Try with this:
Manual installation of iperf3 3.1.3 64 bits :
Linux manual Installation 64 bits sha256
sudo wget -O /usr/lib/libiperf.so.0 libiperf.so.0_3.1.3sudo wget -O /usr/bin/iperf3 iperf3_3.1.3sudo chmod +x /usr/bin/iperf3Manual installation of iperf 2.0.9 64 bits :
sudo wget -O /usr/bin/iperf iperf_2.0.9sudo chmod +x /usr/bin/iperf
The content (NETFLIX, Amazon), which uses the inputstream algorithm, plays flawlessly only up to 720p.
1080p streams stutter and audio gets out of sync, on both S905 and S905X boxes.
No matter of the buffer settings, audio pass-through and etc.
Also,
shutdown from Kodi does not work, from CLI - yes.
Any ideas?
I've bought some "karate" H96 Pro Plus 3/16.
When I get my hands on it, and cooling mod it,
will see what's up with the dtb and remote. 
Meh.
I just did, out of curiosity, to see if the situation is really that bad, or with the latest development it's already at least acceptable. 
Has anyone noticed degraded preformance when using a wired connection?. seems to be constant buffering and files not being served quick enough over Wired but fine over wifi on my system.
On my S905X box with 100Mb Ethernet - 4K content is stuttering, ergo - not enough bandwidth.
AP6330 WiFi is also not good enough.
However,
on the other one - S905 box - the 1GbE works flawlessly. WiFi is AP6330, and I do not use it, read somewhere that this chipset is limited to ~75Mb/s max throughput...
The /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq on my box is 1200000, But on the latest 9 built it's 1512000.
I read in an other post that this cold be temperature related, but my box has a cpu fan attached and the temp is always low.
What is your nominal temperature reading for the CPU in LE?
And in Android?
So,
in my case - none, since everything works as expected from 64 Gb MicroSD LE setup...
All right. eMMC. 
What about the benefits (and drawbacks) of using it? 
What would be the benefits of installing on NAND vs. SD,
apart from the write speed gain?
Is it that crucial, once all Kodi services are loaded?
For example:
And if Kodi storage has to be moved to SD card, because NAND size cannot (wouldn't) handle it,
doesn't that stultify the purpose of NAND install?
I am not acquainted "in-depth" at all what the installtointernal procedure actually does,
and if LE installation is overwritting the Android recovery partition,
but, according to section from the [HOWTO + FAQ] Install community builds on S905/S905X/S912 device
for the revert procedure you'll need the Android recovery image, so I guess it does.
Probably, for the revert procedure - you can use the TWRP image, instead of the "original" ROM recovery one...
In some boxes,
the "reset" function is hidden at the bottom of the AV jack.
For example:
Test if you'll hear/feel the micro button click by inserting a toothpick in the AV jack hole VERY GENTLY, when the device is completely off the power grid, of course.
If yes - proceed forward with the "normal" reset procedure...
However,
is some "karate" boxes,
"vendors" "cost-efficiently" have not installed a micro button
right behind AV,
and you have to open the box and short-curcuit the empty socket pins on the bread-board to reset the device...
For that you'll have to provide the Kodi crashlog.
This would assume that you revert back the setting, which crashes Kodi initially, wait for the black screen and then get the latest
"kodi.log" or "kodi_crash.log" from the following folder:
# ls -lAh /storage/.kodi/tempMost probably there is an incompatibility between Kodi screen settings and your TV HDMI settings.
Here's a list of DX900 screen resolution capabilities:
4:4:4 / 4:2:2 - 30p, 25p, 24p
4:4:4 / 4:2:2 / 4:2:0 - 60p, 50p
4096x2160 - 60p (displayed as 3840x2160)
4096x2160 - 50p (displayed as 3840x2160)
4096x2160 - 30p (displayed as 3840x2160)
4096x2160 - 25p/4:4:4 (10, 12 bit) (displayed as 3840x2160)
4096x2160 - 24p/4:4:4 (10, 12 bit) (displayed as 3840x2160)
3840x2160 - 60p
3840x2160 - 50p
3840x2160 - 30p
3840x2160 - 25p/4:4:4 (10, 12 bit)
3840x2160 - 24p/4:4:4 (10, 12 bit)
-
HDR 3840x2160 – 10 bit colors – BT.2020 color space – 4:2:0 – 75.6 Mbps bitrate – 59.940fps – HEVC ([email protected]) - .mp4 file
HDR 3840x2160 – 10 bit colors – BT.2020 color space – 4:2:0 – 56.4 Mbps bitrate – 23.976fps – HEVC (Main10@L5) - .mp4 file
HDR 3840x2160 – 10 bit colors – BT.2020 color space – 4:2:0 – 60.3 Mbps bitrate – 23.976fps – HEVC (Main10@L5) - .mp4 file
3840x2160 – 23.976fps – 10 bit colors - BT.709 color space – 4:2:0 – 51.4 Mbps bitrate – HEVC - .ts file
3840x2160 – 8 bit colors – YUV color space – 4:2:0 – 50.0 Mbps bitrate – 29.970fps - AVC - .mp4 file
3840x2160 – 10 bit colors – YUV color space – 4:2:0 – 23.1 Mbps bitrate – 50fps - HEVC - .ts file
2560x1440 – BT.709 color space – 4:2:0 – 6.54 Mbps bitrate – VP9 - .mkv file
3840x2160 – BT.709 color space – 4:2:0 – 12.71 Mbps bitrate – VP9 - .mkv file
1920x1080 – 8 bit colors - YUV color space – 4:2:0 – 2.5 Mbps bitrate – 60fps - HEVC - .ts file
1920x1080 – 8 bit colors - YUV color space – 4:2:0 – 60fps - 2.2 Mbps bitrate – HEVC - .mkv file
1920x1080 – 8 bit colors – BT.709 color space – 4:2:0 – 98.3 Mbps bitrate – AVC - .mkv file
So,
you might need to tweak the TV HDMI input settings as well, to match the signal parameters, which the media box is providing it (UHD, YUV 4:4:4 and etc)...
For example:
# cd /storage/.config/
# mv autostart.sh autostart.sh.bak
# rebootAnd do NOT type the "#" symbol, it's just a prompt sign...
Log in again via SSH and rename/remove the ".config/autostart.sh" file.
Reboot and watch what happens.
Try to correct the picture size from the TV picture settings.
Well, create this autostart.sh, reboot, check if the setting is applied on boot:
cat /sys/class/amhdmitx/amhdmitx0/attrand test the UHD HDR 10bit playback.
That is from the media box part.
Do you have a TV/monitor, which supports YUV444, HDR and 10bit?