System updates are in my experience always a challenge. Be it Windows, Mac, or Android. Always need time, patience and tweaking. The truth is that software engineering by far doesn’t follow the same strict engineering quality standards that used to be applied to electrical and mechanical devices, for evident reasons of trying to remain edgy and ahead of the pack at any cost. Battery management is a typical example in modern devices, it’s ludicrous how badly it’s designed under an engineering viewpoint.
So never expect the transition to be smooth. If you do so, maybe you should ignore system upgrades, with all it means in terms of losing compatibility with future apps. Yes, smartphone ecosystems are a b*tch, welcome to the real world!
Personally I’m still waiting for the moment when I’ll have time available to do the upgrade, and I immensely thanks Fairphone for allowing my device to remain functional much beyond what any other brand would allow me to. And I also thanks all the tweakers that will make my own upgrading process much easier when I finally do it.
For the unlucky upgraders, a simple advice: think about resetting the data of your apps one by one, or start from a clean installation of the new system. You probably have a deep incompatibility between an app that still thinks you are in Marshmallow when the system is Nougat, and it wasn’t configured correctly for Nougat.