W10 File Assocoiation Issue for "Photo viewer" not working properly

[Hurky]

Hi,

All was well and then, all of a sudden (Dec 16th 2020?), I started having problems with pictures / photographs and their association: Nervous Flickering of icons, some "flickering everywhere" and a slowing down of the system.
I investigated mostly on the Microsoft Fora and a bit otherwise and in the end I removed:

• IrfanView (64 bit version),
• Microsoft Photos

I then reinstalled MS Photos and: Nothing: Same issue of flickering of icons, a nervous screen and slow performance remains.

When I choose "Microsoft Photos" as the "Default App", the Settings Screen disappears (it just pops away) and when going back to the "Default App" environment, the "Photo viewer" remains "+" in a grey background, no app associated.

Going to "Choose default application by file type", doesn't work either: It never ever gets to generating the list; been waiting for over 30minutes,

I so much do not want to reinstall Windows... What to do?

I'd rather prefer having IrfanView back again.

Thank you in advance for helping me (and maybe others) out,

Hurky

[Jameswalter2050]

Update Windows Photo Viewer. If you're using an older version of Windows Photo Viewer, it may not be compatible with the latest versions of Windows 10. To update Windows Photo Viewer, open the Start menu and search for "Windows Photo Viewer." Right-click on the app and select App settings. In the App settings window, click on the Advanced tab and then click on the Check for updates button. If there are any updates available, Windows will install them automatically.
Reset Windows Photo Viewer. If updating Windows Photo Viewer doesn't fix the issue, you can try resetting the app. To reset Windows Photo Viewer, open the Start menu and search for "Windows PowerShell." Right-click on the Windows PowerShell app and select Run as administrator.