So I got my Cherry G84-4100 and right away I noticed the sticking issue many other people have noticed: if you don't hit a key dead center, and especially if you hit it on a corner, it will "stick" for a moment before going down. This is claimed to happen with all Cherry ML switches.
Messing around I found that this sticking actually doesn't go away until you shift the force of your finger. So right away I knew it wasn't a friction thing.
Removing a keycap and messing around... and noticed that the switch wasn't sticking! Even if I pushed a stem on its far corner, it still wouldn't stick. Then I compared to the other keys; they still stuck.
I looked at the bottom of a keycap and it struck me. It's a keycap design problem! The keys have too much vertical give; ie, if you hit a key at its top or bottom it will tilt. The sticking doesn't occur if you hit a key on its left or right side (or at least not nearly as much), only if you hit it on the top or bottom.
The keycap tilting stops it from actually depressing the stem, and thus prevents the key from actuating. Hence sticking.
The reason it tilts, I believe, is because the two plastic tabs that hold the keycap in place to the switch are not snug. Thus there's too much wiggle room, and the key can tilt. Presumably the caps are made this way for manufacturing reasons or something, or maybe they were just overlooked. I don't know. But maybe... Could it be possible to modify the keycaps so that they aren't free to tilt?
Regardless, I think the problem isn't with the ML switch itself, which appears to be sound, but with the design of keycaps used with this switch.
