2016 rMBP w/TB: Keyboard spaces issue

It might be related to the other keyboard issues that Mac's with the butterfly keyboard experience.

In short it is moste likely some debris stuck underneath the spacebar which can provide enough pressure to register a keystroke. Apple has released a support document tell you how to clean the keyboard with compressed air, other forum members have had luck with other approaches, while some had no luck at all.

I would recommend looking into some of the other keyboard threads here

Apple keyboard cleaning guide
https://support.apple.com/en-us/HT205662

 

You can also pop the spacebar off. There are youtube videos demonstrating how to do this. The keys are very fragile though, but once you have the technique down it's foolproof. I've probably popped off about a half dozen keys now without damaging anything.