With use the vac end becomes more loose. I have to replace them every 3-4 years. Mine comes loose when I use it with my DTS400 or ETS125 because they have small dust ports. But my old sloppy one does not come loose with the RO150, ever, because that one has a very long dust port that sticks deep into the nozzle.
Festool is already aware of this, because they have already released an updated version that locks in place. Though some people here on the FOG are not so charmed about it. I myself haven't used it yet.