I have also created a post in which I described a similar issue. My phone dies even with 7% or 9%, I have to be careful not to allow it to drop to that percent and always have my Samsung Power Bank near by. Apparently the battery itself is fine and healthy.
I simply do not allow it to drop under 10% anymore. I have received advice to do a factory reset or take it to a Samsung Experience Store (which would also imply a factory reset) but to be honest it's too much hassle to re install it and set it up again. I will slowly learn to live with it, until I change the phone altogether.