Hi Christian, Have you recently descaled/dacalcified the machine? Also have you tried cleaning out the group head? For an instructional video on cleaning out the group head, please click the following link: http://www.wholelattelove.com/videos.cfm?playvidID=601. If that doesn't resolve the issue, and it is still leaking around the top edge of the portafilter basket, you might want to buy a new group head gasket. You can find a link to the group head gasket here:https://www.wholelattelove.com/Gaggia/gaggia-11004543.cfm.