Had the roof resprayed as part of the latest hail damage repair on my white van.

After about 5 months when the weather started to heat up I noticed cracks opening up in both gutters...wear the welds/seams run...and they kept opening...to the point where they were close to the full length of the roof. It was diagnosed as having too much paint in the gutters which dried on top faster than it did underneath. Like mud at the bottom of a big puddle. So it was sanded back and resprayed.

Another 2 months and the cracks started opening up again. So this time after it was sanded back they applied body deadener before spraying. They did a pretty poor job of applying it and didn't smooth it all down properly.

Yet another 2 months and now more cracks are opening up. Less than before and smaller. It looks like they are above the areas where body deadener was applied.

A VW mechanic advised there is some product that should be put down in the gutters before painting? But he couldn't remember the name.

Has anyone else experienced this?