https://techcrunch.com/2018/07/19/apple-reportedly-confirms-keyboard-reliability-fix-in-internal-document/ > An internal Apple document distributed to Apple Authorized Service Providers and obtained by MacGénération and MacRumors confirms that there’s a membrane under the keyboard to “prevent debris from entering the butterfly mechanism”. This is the first time Apple acknowledges that the third generation butterfly keyboard tries to fix unreliability issues. > “The keyboard has a membrane under the keycaps to prevent debris from entering the butterfly mechanism. The procedure for the space bar replacement has also changed from the previous model,” the internal document says.