Same here, "B" is double typing. This is on 2016 MBP with 2017 keyboard model (been replaced under the warranty before). Warranty expired now, no help from apple.
So I had to glue it for it to hold, but the butterfly part which I ordered was from 2017 model (mine is 2016) so the key was lower and didn't work properly in the corners. But it solved my double click problem and I been happy with it for a while. Later I got same double click on another key and had to replace my keyboard under the warranty. I got new 2017 keyboard model and new battery as a nice bonus. 2017 model is much better so I would highly recommend anybody with such issue to replace the whole keyboard.