Hi Remi,
Thank you for posting your query in Windows 10 Technical Preview.
I understand that you are facing issues while installing an update and getting an error 0x80200068, while installing it.
I suggest you to follow the steps below and see if it helps:
Disconnect all external devices connected to the Surface
I suggest you to remove all the external devices connected to the surface and see if the issue persists.
Disable Firewall and Security Suite
If you are using any 3rd party security software and firewall, I suggest you to temporarily disable it and try installing the update.
Note: Antivirus software can help protect your computer against viruses and other security threats. In most cases, you shouldn't disable your antivirus software. If you have to temporarily disable it to install other software,
you should re-enable it as soon as you're done. If you're connected to the Internet or a network while your antivirus software is disabled, your computer is vulnerable to attacks.
Hope this helps, do let us know if you need further assistance with Windows.