The B key had a similar issue on my 2016 MBP with Touch Bar, sometimes it wouldn't register my presses and other times it registered two presses. I took it in for repair, and indeed the whole top case was replaced. Now the B key is working again.

However other keys randomly feel "smushy", "not clicking" as I press them. There can't be any dirt in the keyboard, I'm very strict on keeping my keyboards clean. Until now, the issue was resolved by bashing the keys a few times on all corners. However I'm worried that the keyboard won't last as long as to be expected of a laptop.

Yay on the repairability and reliability of these new keyboards.