Mine's been doing that too, I ordered a new ring which has disappeared in one of the moving boxes we still haven't unpacked after a year. I'm fairly sure a new O-ring will fix it, but it hasn't bothered me enough to start digging through the 'miscellaneous' boxes.
Likely just the two little bolts holding the group on need tightened a bit. Don't think I've replaced that O-ring yet and mine is just over 3 years old and used daily.
Europiccola question:
Steam escapes / bubbles from the joint where the grouphead bolts to the boiler when I pull a shot.
It's relatively new (<1yr old), there's no build up of limescale or obvious degradation anywhere.
Do I just need to replace the O-ring?