What do they use on the spacebar anyway? My understanding was that the Duckys with browns had a black switch there (unless I'm mixing things up). I doubt we have a grey one here, at least I can't imagine anyone complaining about it being too light.
While linear MX switches are the most likely to exhibit accidental double presses, there shouldn't be that much key bounce. This may indicate either a soldering problem (as mentioned) or a "bouncy" switch contact that possibly could use a bit of bending or just replacement.