Watch screen carefully an eventually it will say sorry fat too small. must be greater than 512.
As far as I know, LibreELEC still works fine with a 512MB system partition. Also on Generic.
Perhaps you are trying to install or upgrade with a different LibreELEC community build with extra features?!?
What is the version of the current installed old LibreELEC?
Simple instructions would be greatly appreciated.
This all depends on what device you have LibreELEC installed. Most devices use SD cards these days, the generic PC builds of course use harddisks or SSDs.
- Make backup of your current setup via the built-in Backup/Restore tool. Put backup file in a safe external location.
- Install LibreELEC 9.0.1 fresh onto the SD card
- Choose to either create a new setup, or restore the old backup. Depending on how old your previous Kodi/LibreELEC setup was, this might give problems. Also, the latest LibreELEC/Kodi version uses a newer database version... Starting fresh is recommended I'd say.
if I can't boot the system
You'll have to downgrade of course for that. 
I don't care about settings, addons or anything else. just my video and music library.
Pull the SD card from the RPi, run a Linux Live session on your PC (f.e. Ubuntu, because of LE's EXT4 storage partition), and copy the database files to a safe location.
Have you tried Kodi's internal NFS source options? Via browsing to NFS servers?
A Raspberry Pi, even a v3, is still a slow-as-hell device when it comes to CPU intensive tasks. => high CPU percentages.
Add to that the average SD card that has a lousy write speed compared to reading speed, and you just want to let the Raspberry do its thing. Let it work through the night if necessary and hope that everything goes well.
If you have stopped the process anyway, make a backup/copy of the current old database(s) and store it somewhere safe.
Can I just copy the Userdata" folder via Samba and then restore it to Kodi?
Copy, yes. Restore, no. What would be the point in doing that after upgrading?
A different backup: do a Video Library Export with separate files, so all metadata info will be stored in .nfo files next to your video files. Don't forget to activate the watched status and resume point options first.
The RPi does not do every video with hardware decoding. HEVCon the RPi is done via software decoding using various tricks.
Did you try the option to add a network source via "Add a network location.." ?
why the hell is it listed as a feature in the release notes?
Because, my dear Watson, those are not official features. And will likely never become official features.
You can find multiple threads on Netflix and Hulu on the Kodi forum as well.
BTW, it's kernel, not kernal.
If it's an OpenELEC based device, the system partition size is likely too small for LibreELEC now.
If (for whatever reason) the box doesn't allow for the storage drive to be re-partitioned, you will now have an additional book end on your shelf.
otherwise you have to use a data recovery tool
Don't sneak in a link to a commercial product in your first forum post.
It will get you put on the forum moderators' watch list.
In my world, "the best server" and "Windows" are words which are not often spoken in one and the same sentence. 
If one Kodi device is able to connect to your Win10 PC, so should any other (Kodi) device. Otherwise, your settings in Windows 10 are probably not optimal. Perhaps you have limited the amount of users permitted to connect to your server to '1' ?!? During the last 12 months, lots of changes have made SMB go from good to better, or from bad to worse, judging from all reactions of Kodi Samba/SMB users. SMBv2 requires a Windows share to have full credentials, including a password.
SMB and NFS are the two most suitable file protocols when it comes to streaming over a local network. FTP is not an option for that in my book/network.
Alternatively... If you have some old PC collecting dust somewhere, on a rainy weekend try installing Ubuntu Linux on it as an OS, instead of Windows. And then install NFS server for a couple of videos as a test setup. There are plenty of tutorials for that to find. And once it runs, it runs and runs and runs. My NFS file server already worked with XBMC Eden, some 7 years ago. 
Any suggestion on what to do?
If I ever use mkvextract, I use it on a non-htpc (linux) computer, and not directly one of the Kodi client devices.
I'm using a bash script with a couple of parameters to simplify mkvextract usage even further for auto-placing the files in the correct location.
any insight?
Not really. No useful technical video info (we're not Handbrake experts), nor a Kodi debug log was provided. The log itself consists of more than 3 lines. We cannot see your log file from here.
Enable debugging in Kodi, restart LibreELEC, play the problem video(s) and provide the log file as per the following instructions.
2018-06-22 13:11:53.731 T:1937259376 NOTICE: Disabled debug logging due to GUI setting. Level 0.No debugging was enabled. See my previous post again for all instructions.
Yep. Should be fixed in the next Kodi version.
Why would you need calibration anyway?
What is your display, and old CRT monitor/TV ?
Every recent TV has its own settings for a 1:1 pixel display, and in that way, disabling overscan.
Using calibration should be the very last resort for solving these problems.
Strange... I've used a Wetek HUB from its beginning, and I use a Ubuntu from 10.04 on with NFS as servers for years. I've never seen big pauses like that. Perhaps your file server has hiccups after a bad update? I take it you use your Wetek HUB via an ethernet cable and not wifi?
Also we're never happy with only 2 lines of the log file, we need the full picture for decent trouble shooting. so always provide the complete log file via a pastebin website.
IMO the "+" character shouldn't even be there as per Kodi's default file naming convention. Just remove it.
As we still not have a crystal ball in our tool box, you'll have to help us a bit.