Like others here, I'm starting to think it has to do with a combination of heat generated by the computer, the stainless steel dome switch, and -- in the case of the 2018 models, especially -- the silicone membrane.
I wonder if the membrane embedded into the casing is susceptible to warping or expansion in the presence of heat. To drive this point, consider external keyboard covers: have you ever noticed that, over time, they lose the ability to conform to the shape of the keys? I ask this question because when I had an external keyboard cover for my previous 2017 nTB MacBook Pro, I noticed it had stretched out and even *warped* in some places. I suspect this is a result of the keyboard's thinner profile: the cover is is now closer to the top case and, in turn, the heat coming from the computer, leading to the above. When you then effectively embed a keyboard cover into the chassis itself, I'm willing to bet these effects are amplified, leading us to seeing this phenomenon much sooner.
Then consider how the heat might affect the dome switches: metal expands and contracts as it heats and cools. I suspect this and the thin profile of the switches likely leads to imperfections in the switches themselves, thereby affecting how the key hits the contact on the board. Depending on the thickness of the switches and how these imperfections might manifest (maybe causing deviations in the geometry of the switch), this might be why some keys double press or fail entirely.
Putting these two problems together à la the 2018 MBP might ultimately explain why, even with careful usage, some are getting these failures weeks or months into ownership while some are fine. Regardless of whether it's caused by deviations in manufacturing processes/standards or what have you, I really do think all of this points to an overall structural problem with the keyboard.
Here's Apple's own comparison of the switches, for reference.
This is all speculative of course, but I can't help but think this is why.
I wonder if the membrane embedded into the casing is susceptible to warping or expansion in the presence of heat. To drive this point, consider external keyboard covers: have you ever noticed that, over time, they lose the ability to conform to the shape of the keys? I ask this question because when I had an external keyboard cover for my previous 2017 nTB MacBook Pro, I noticed it had stretched out and even *warped* in some places. I suspect this is a result of the keyboard's thinner profile: the cover is is now closer to the top case and, in turn, the heat coming from the computer, leading to the above. When you then effectively embed a keyboard cover into the chassis itself, I'm willing to bet these effects are amplified, leading us to seeing this phenomenon much sooner.
Then consider how the heat might affect the dome switches: metal expands and contracts as it heats and cools. I suspect this and the thin profile of the switches likely leads to imperfections in the switches themselves, thereby affecting how the key hits the contact on the board. Depending on the thickness of the switches and how these imperfections might manifest (maybe causing deviations in the geometry of the switch), this might be why some keys double press or fail entirely.
Putting these two problems together à la the 2018 MBP might ultimately explain why, even with careful usage, some are getting these failures weeks or months into ownership while some are fine. Regardless of whether it's caused by deviations in manufacturing processes/standards or what have you, I really do think all of this points to an overall structural problem with the keyboard.
Here's Apple's own comparison of the switches, for reference.
This is all speculative of course, but I can't help but think this is why.
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