Edging strip on the edges of panels werever it passes near an edge. Some at the top of the hatch I can see in the photos. I noticed you put some cover on the pipe in a few places but also put some edging strip on the metal holes. Check in the rear quarters too our ibiza had some edges up there when I renewed its pipe a few years back with standard washer hose like you have. You may have simply blown the pipe off. I had to cable tie the joints to stop it blowing off in the winter.