I constantly ran –allow-vendor-change in openSUSE Tumbleweed. I had installed extra codecs with the OPI commando and always had problems with media files, mostly in Firefox. Also, I installed Kvantum and bugged some themes, disabled Akonadi and KDE was acting weird, etc.
Finally, I decided to delete the openSUSE partition, allocate more space (reducing Windows partition) and then reinstalling. I’m good now :)