"Unfortunately, Apple's butterfly-switch keyboards have a troubled history of failure — littered with users shooting compressed air at stuck, unresponsive keys. There have even been a couple of class-action lawsuits.
...
Apple's been decidedly mum on the reliability of its 2018 MacBook keyboards. From what we've seen, though, Apple is trying to fix the situation: leaked documents explain how the 3rd-gen keys have a membrane layer (the existence of which was confirmed in an iFixit teardown) under the keys would protect the switches from debris. But flaws, apparently, still linger."
https://www.laptopmag.com/articles/2018-macbook-air-keyboard...
Users reporting problems here:
https://www.reddit.com/r/mac/comments/9x700s/new_macbook_air...