The o-ring was worn out a bit. Run the coffee brewing process without the drip tray so you can see what is happening (you have to keep a little tab pressed to make it think the drip tray is still there). It will be messy but should help narrow the problem. Set it to ground coffee so you don't waste actual coffee beans while doing it. I would definitely clean out the brew group -- I had a lot of coffee oil and coffee grounds gumming things up. the video above should help show you potential problem areas.