Did you do a factory data reset after the update? If you look through the multitude of OS update threads over there years, you'll see that this is a frequent occurrence across all make/model smartphones. It's usually not required when doing the smaller "maintenance" or "bug fix" updates, but when taking a major update from KitKat to Lollipop, Lollipop to Marshmallow etc etc, it's strongly advised to perform a factory data reset after you've received the update.
I know that's not the answer you wanted to hear, but I can assure you it's standard operating procedure to do so, and it'll resolve a multitude of problems. Granted some folks can get away without doing it, and oftentimes problems won't crop up until later down the road, but your best bet is a FDR. (Especially since you're experiencing more than one problem)
Of course don't forget to back up your contacts, files, etc first.
Good luck & let us know how you make out.
S5 tap'n