I had a look at the CPU data sheet, max. frequency (burst) is 2.30GHz, so 800MHz is not close to the max, as I stated before.
The data sheet of the NUC says, it supports two displays (HDMI, VGA). Maybe one of them has to be switched off to relieve the CPU.
* see my next post *
You are not using a stable build of LE. Try a major release, like 9.0.2.
It does not explain 800Mhz Max on the CPU.
I don't think so. A memory leak can explain high CPU usage. Follow my advice and post the result.
It looks like a memory leak error, triggered by the Netflix add-on:
...
2019-07-26 10:10:42.314 T:139900012103424 ERROR: EXCEPTION Thrown (PythonToCppException) : -->Python callback/script returned the following error<--
- NOTE: IGNORING THIS CAN LEAD TO MEMORY LEAKS!
Error Type: <class 'urllib2.URLError'>
Error Contents: <urlopen error [Errno 111] Connection refused>
Traceback (most recent call last):
File "/storage/.kodi/addons/plugin.video.netflix/addon.py", line 33, in <module>
NAVIGATION.router(paramstring=REQUEST_PARAMS)
...Uninstall the add-on and see whether it solves the issue. Maybe a simple re-install makes Netflix work as expected.
Hard to say with the provided data. Please give us a link to the log file. Always use the default skin for all tests.
Welcome! 
I'm from Germany. Where are you from?
For example on a cable here : Câble HDMI 1M - KUBII
Wrong product. If you want 4K, then go for a store that clearly says "4K". It's easy to find.
Official HDMI standard names are "HDMI High Speed" and "HDMI High Speed Premium". They both support 4K.
You need a fresh installation. Avoid to install data into bad blocks of the SD card (I bet you have some). To do so, GParted can identify those bad blocks, and leaves them out on the format process. e2fsck can't do this, and it can't bring the data back that you have already been lost.
It doesn't makes sense to talk about follow-up errors now. Replace or repair the SD card first. Repair is possible, but I only suggest it for advanced users, who can deal with special software tools like GParted.
I think so, too. SQUASHFS is read-only, and when a read-only FS throws errors, then a broken storage device is the first idea.
So if I understand correctly, whatever the micro-hdmi adapter to hdmi, I would have no loss it has no impact on the flow etc
As for the cable, I just take a hdmi high speed cable in the title and they are all compatible HDR / 4K 60FPS? Or not specially?
It's all about electromagnetic shielding. The higher your screen resolution is, the higher the data transfer rate. There are no additional electronic parts needed.
My Pi 4 is not in a case yet and that's fine.
That's the trick - heat moves upwards. People with a closed case on top (like the official one) are in trouble.
A small adapter (maybe metal case for shielding) and a regular (high speed) HDMI cable is the best (most flexible) solution. The adapter leads all signals from source to target by simple wiring.
I don't have an RPi4, but I know your first question has been discussed here. That's the thread to go for, when it's about RPi4 news.
If you don't want an install from scratch, use GParted to enlarge the FAT partition as suggested. 1GB should be fine.
You got a lot of external add-ons from inofficial repositories. Maybe one of those updates content as you know it from a cron job. Are you sure your add-ons are completely legal?
Yes, it's a known change when upgrading to LE 9. This should be the fix.
