For me it was dust under the Q key, not a common key. I don’t see why dust is more likely to land behind the most used keys either. Also that redditor concludes

For me it was dust under the Q key, not a common key. I don’t see why dust is more likely to land behind the most used keys either. Also that redditor concludes by saying the cause is unknown. I haven’t had any keyboard issues on my 2016 and 2018 models since I regularly started air spraying the keyboards.