I contacted Siggi about my "drooping corner" and he believes that the spring isn't broken but perhaps has gone inside the pole itself. This may have happened when the section slipped once. The drooping corner has been getting worse and this may be caused by the spring moving further into the pole section.
Siggi suggested opening the unit but leaving the "Y" poles down, pulling the pole out of the section at the "Y", retrieving the spring out of the pole and reinserting, perhaps with a washer to prevent the spring going inside the pole again.
I can't open up the unit until Saturday in Cornwall

so I'm going to take a selection of washers with me from hubby's toolshed and see if this works. I'll let you all know.
Pete, your reply seems to be in respect of an Easy, rather than a Venezia. Your pictures for replacing springs certainly show Easy setup for the poles.