I have a most peculiar problem with my nokia 8. The volume - button stops working. At first I thought it had to be a hardware problem, I sent it to repair, got it back, it worked for like 8 hours, then it stopped again.
In the mean time, I learned that after a factory reset, the button starts working properly again, but after a while, SOMETHING makes it stop working. I am not sure if it is an update, an app intercepting the button or somewhere, something at the OS level intercepts the button's signal and does God knows what unclean things to it.
Once the button stops working, there is nothing that will make it work again, except a full wipe of the phone. My guess is that some flag gets set in the OS and disables the button.
If there is of any help, this started happening after the march2018 update.