Nothing so far and I insisted on shutting down the computer with Opera opened every single time. There's nothing wrong with that and it seems that this isn't what is causing the problem.

No new version folders in the installation location, no problems yet. I can clearly see where this is going, but I'm waiting for it to happen to have a clear confirmation.

I totally see what you mean, but it would by the first application to have problems with forced shutdown on Windows in years, at least for me. I'm on a laptop too, so I have my lid close action to shut down, and usually when I'm done with the day I just slam the lid down.

I will continue observing and I'll come back with details.

I'm glad I found a place to get help with this.

Don't know if it's the cause but shutting down the computer with programs running is not recommended since it may lead to such kind of issue.

That was back in the Windows XP days, nowadays the OS takes care of this, since the times of Win 7. Have you never seen the "X programs are still opened and you might lose data - WAIT/SHUTDOWN ANYWAY" screen? All software is gracefully shut down by the OS.

If this is an issue, then its a new problem that needs to be solved by itself, as Windows 10 is definitely not doing it with other software.

If you do some changes, close Opera and then reopen it, are the changes kept?

Yes! No matter what. Until the day it decides to reset itself.

Is the "Bookmarks" file stored in the same folder as settings and extensions? Leo? If so, it's weird. Unless there's synchronisation involved.

Yes it is. No sync involved at all.

Mr Ro, you tried uninstalling? You said "Portable" - it worked well?

I had the classic install. It started behaving like this, then I tried portable, no difference whatsoever.

Are there settings that are kept intact?

Settings, no. If you refer strictly to Settings, they're all gone.

What's your anti-malware dude there? Any additional cleaning software? Registry boosters? Optimisers?

I use F-Secure Antivirus (no specific reason other than that I had a free license as a gift for a printer I ordered at my local IT shop).

Scanned for other bad stuff with ADW Cleaner.

I am an IT guy, so I don't use stuff like optimizers and boosters and such.

One thing I noticed it's that Opera creates folders named after the version where each version's exe is started after an update. First of all, this seems to be a stupid thing to do if you ask me, and might lead to such problems, why not just replace old files/delete obsolete ones/add the new ones?

The last folder was created today when the problem occurred the last time, I will track to see if it's linked to these folders being created.

This has been happening continuously for more than a month now. Update after update, it still happens.

What I find connected with this behavior so far: it appears it happens when I shutdown the computer with Opera still running (maybe, not exactly sure yet).

What I tried: I tried switching to Opera Portable to different installation directory on rather than the classic Windows system location. I excluded in antivirus. Scanned for viruses/malware. SSD is relatively new (under 1 year) and OK.

What happens: all extensions get deleted, start page gets reset to default (including wallpaper), all settings get reset to default, bookmarks bar is disabled, but bookmarks remain the same. If I reinstall my extensions, they all keep their settings.

Event Viewer is completely silent.

It's a real shame because so far, Opera is the only browser that performs well and outclasses by far any other browser out there, but if this keeps happening, I'll have to move on.