Hey Guys do you come across this often? I've had it twice now and not sure why it's happening. I found it on a service /inspection of the boiler, which is still working fine- which is the puzzling bit. Any clues and what a pain to try top replace, as you can't get to the AP hose connection without taking all the bits out... Have to go back customer delighted, have trimmed crunchy bit of hose to soft bit an re-attached.