The upgrade was smooth and pretty clumsy. No one told me about the risks that could follow. Unfortunately/fortunately I was about to get into the insider ring when the announcement about the update came through. Just updated right away, only after uninstalling virtually all the apps that came with device.
After this installation, l lost all my contacts. Fortunately I'd stored them elsewhere. That's about my experience on the Lumia 640 xl dual sim.