Same issue here and only when the computer is warm. Within a few hours of using my Late 2016 MacBook Pro 15” with Touch Bar, I noticed some of my keys made a very high pitched click on-key-up (when I lifted my finger from the pressed down key). The affected keys: Caps Lock, left Option, and very occasionally: Delete, ‘H’, and ‘C’.
Caps lock is by far the most reproducible for me (will make the high pitched click on 95% of presses). Whenever the key stops making the high pitched click, I can always get it to start again by making a long key press with a little bit of pressure. I can only reproduce the high pitched click on the left Option key on about 25% of presses, and I’ve only noticed it on the Delete, ‘H’, and ‘C’ a couple of times (<1% of presses).
I’ve recorded a video of the issue occurring for my Caps Lock key. I press the shift key 4 times to give a baseline sound for what the key should sound like, and then the Caps Lock key four times to demonstrate the issue. I did the same thing again, but just recorded the audio (the sound quality is a little higher than the video).
Video: https://www.youtube.com/watch?v=48C9eAOCaYE
Audio: https://www.youtube.com/watch?v=u6FCXj9RDKg
It’s important to note that I have not been able to reproduce the issue on any of these keys when the computer is cool.
Since I’ve remapped my Caps Lock to a delete key and thus use it often, I’m very sad to say I’ll be returning the machine.
Note for others: it can be difficult to reproduce the issue on demand due to the possible reliance on heat. To heat up your computer, you can open the application “Terminal”, type "yes > /dev/null & yes > /dev/null & yes > /dev/null & yes > /dev/null & yes > /dev/null & yes > /dev/null”, and press enter. This will spawn 6 processes which just essentially print “yes” really fast, and should cause your computer to hit 75% CPU utilization if you have 4 cores, and thus heat up after a couple minutes. When you want to stop the processes, open a new Terminal window and type “killall yes”.