Cubase 8.5.15 Loses All Preferences

Periodically, when I launch Cubase, I discover that ALL preferences of all types are simply gone.
It takes me hours to completely configure Cubase to my liking.
This is extremely discouraging.

Examples of preferences that are lost:

  • VST Plugin Manager custom collections - my custom collections completely gone, no evidence they ever existed!
  • Track controls settings - all customizations to tracks and mixer gone - reset to defaults
  • Keyboard shortcuts - gone
  • Preferences from File > Preferences - all gone

This is now happening with increased frequency - e.g. twice this week alone.

I have installed new plugins from Native Instruments recently.

How can I at the very least reliably back up ALL of the above settings? I see lots of individualized places where I can save ‘presets’ for a given collection of settings, but I need a place to back up everything.

And most importantly, I would prefer that Cubase not simply destroy all my work!