Is it possible to uninstall a problematic Microsoft update on Windows 8.1, and how?

Yes, you can uninstall problematic updates on Windows 8.1. Open Control Panel > Programs > Programs and Features, then click 'View installed updates' on the left pane. Locate the update (often identified by its KB number), right-click on it, and select 'Uninstall'. Be cautious, as uninstalling certain updates might affect system stability or security, and a system restore point is recommended before attempting this.