Definitely worth keeping an eye on that mount. It seems to be the shortest lived one. My missus's MK4 1.6 used to have the same clunk on gear changes, and when cruising along at a steady speed, just touching the gas or backing off made the gear stick twitch.
I grabbed her engine and rocked it back and forth, and the movement at the gearbox end was hilarious
It was pretty much just hanging there. The rubber had hardened/perished and retracted away from the metal. New mounts from the dealer and all sorted