As we have discussed on numerous occasions, the keyboards have been plagued with reliability issues, including keys that become stuck or fail completely after regular use. In some cases, a single speck of dust is enough to "kill" a key, resulting in an expensive keyboard replacement.
Over the years, Apple has made refinements to the keyboard -- including the use of a silicone membrane to prevent debris from entering the key mechanism -- but that hasn't completely stopped the problem. The class action lawsuit pertains to all MacBooks produced since 2015 and MacBook Pro models built since 2016.
According to Judge Edward Davila, Apple did not do due diligence in providing an "effective fix" for MacBook computers afflicted with butterfly keyboard issues. The reason for this determination is that even with Apple's no-cost replacement program that was instituted after the complaints piled up, defective keyboards are replaced with the exact same part when brought in for service. So instead of actually fixing the underlying issue, Apple is in effect kicking the can down the road, after which the customer will likely have to undergo another keyboard replacement.
After four years of complaints about the butterfly key design, Apple finally got the hint and introduced the 16-inch MacBook Pro that adopts the previous scissor key design. By reverting back to the old design, the 16-inch MacBook Pro is slightly thicker, but the keyboard reliability issues will hopefully become a thing of the past. It's likely that the scissor key mechanism will be adopted by the next-generation 13-inch MacBook Pro in 2020 and eventually make its way to the MacBook Air.