i still think something might be corrupted with your vivaldi folder inside .config/
if you purge i dont remember if youll lose the profile data/folder.
make a backup of the vivaldi folder inside .config if it isnt too late, or just rename it.
you might also try booting into the recovery console at boot and try checking the filesystem for errors for disk containing home.
have you noticed anything else weird lately like corrupted downloads or files in general? ram and or ram slot going bad could be to blame. i had that happen once.
in any case i highly recommend timeshift if you have spare storage space. it has saved me a couple times when packages got boogered up.