Slight click between gear changes

I have a CR150 CRBC engine Golf with the DSG box, it was serviced about 2 years ago now and ive never had any issues with it but recently i've noticed a click or knock between gear changes usually 2-3 3-4 under low load. I'm not convinced its gearbox because it doesnt always happen but i'd be interested to know if it may be, in the mean time i've order a new alternator pulley and belt as it sounds to come from that side of the engine and may be the pulley not running over when needed. Any help appreciated thanks.

Could be one of a number of problems