I put two rivets in a pipe on my Saaaaab when it used to do that, just for something for the jub clip to rest against, supposed temporary solution that lasted forever.
On the Portia - I concur with @danstuff, sounds like a collapsing or swelling flexi hose.
I've used pop rivets on water hoses, before I got a TIG welder that could do AC so I could weld ali, but on an induction pipe I worry (almost certainly without any justification) about the end of the pop rivet coming off and getting somewhere it shouldn't.
I put two rivets in a pipe on my Saaaaab when it used to do that, just for something for the jub clip to rest against, supposed temporary solution that lasted forever.
On the Portia - I concur with @danstuff, sounds like a collapsing or swelling flexi hose.