I had a macbook pro 2016 and had problems with the key "b", which produced "bb" about 1/3 times I hit the key. After reparation and several months later, I had the same problem with the letter "n".
I now own a macbook pro 2017, and I feel I have the same problem with the key "m", but maybe with an occurence of 1/40, which make it much harder to demonstrate.
It's always the same zone on the keyboard, I was wondering if several people had the same problem ?