My left commend button became unreliable a couple of years ago and the lettering on the A and S keys faded. Took it in several times and was denied help until Apple launched their keyboard replacement program, at which time they replaced the top case for free in August 2018. SWEET!
A and S started to fade about six months ago:
the left command key started flaking two months ago, and for a new and exciting addition, the far right edge of the touch bar started to flash solid white light about a month. Now the touch bar is taking a steady, right-to-left death march. I still get the flashing white light at the right edge, but the touch bar is now completely dark from the right edge to the 9 key to the flashing light:
…and it’s moving faster - about an inch in the last two days.The touch bar buttons work, but they are not displayed.
So looks like this machine will need another top case replacement after a year and a half, about as long as the first one lasted.