Anyone else had trouble with manually selecting gears at times?

A few times lately, the car just hasn't shifted when I've done a manual change either through the stick or through the paddles. First couple of times it wouldn't change to 6th at 60km/h, but needed to get to about 67-68, then today it wouldn't downchange to 3rd while slowing down at about 70km/h..

It only had the 30,000km service about 3 weeks ago, and they advised everything on the gearbox was fine... even though I still think it has its rough moments..