I thought I was losing my mind - I've been experiencing the exact same thing with the MX keys/mouse over the past few months, and no amount of fiddling or reinstalling has been able to fix it. My scroll wheel regularly gets "clogged up" too, becoming unresponsive for 5-10 seconds, then dumping out all of my buffered scroll data at once in a furious explosion of scrolling. It's quite frustrating, and I've been looking forward to a fresh install of Big Sur to hopefully flush out whatever gremlins have been gunking things up.