[RomMon]

The settings in /storage/.kodi/userdata/guisettings.xml get reset to their defaults after Kodi 17.1 froze due to /storage (~/) was full, and I rebooted the Rpi.

Rpi3
(128 GB flash)
LibreElec 8.0.1

I observed the same issue November last year (Kodi 16). (This time I was prepared by having the add-on 'Backup' in use, taking a weekly backup.)

Is it known that a full home-directory can cause loosing all non-default guisettings.xml settings?

[Milhouse]

Is it known that a full home-directory can cause loosing all non-default guisettings.xml settings?

Yes, and hardly surprising - when you shut down Kodi it writes the guisettings.xml file. If there is not enough space on the file system you get an empty or truncated file. When you next start Kodi it loads the empty/truncated file, realises it is garbage, and uses default settings.

I'm sure there would be ways for Kodi to avoid creating an empty or truncated guisettings.xml on shutdown, maybe raise a trac ticket.

[RomMon]

Thanks for confirming the observed behavior.
Opened a trac ticket: https://trac.kodi.tv/ticket/17451