I'm not sure if I'm describing it properly, but on the end of the portafilter is a piece with the Rancilio logo on it. The piece comes off to reveal the nut/screw that secures the portafilter to the handle.

This piece comes of very easily now, to the point where it comes off in your hand when tightening/removing it.

How do you secure it better? Would some plumbers tape around the shaft do the trick to provide some resistance? There appears to be some white residue on it, so I'm not sure if they use a light glue to hold it in place from the factory?