Primer will shrink MUCH faster than paint in most cases. A cheap primer (laquer primer) is simply a gray filler mixed with laquer. Laquer evaporates at an extremely high rate, and this is why primer tends to dry faster. This can create 2 problems....
Primer applied TOO dry will create a surface that acts as a sponge. REALLY bad on the paint basecoat and the paint loses surface since it is sucked into the primer.
And primer that has too much laquer tends to remain wet under the surface and this can create serious internal problems (most likely what has happened in this case).
It is essential that, first off, the right primer be used. If your cladding is painted, a laquer primer is the WORSE possible thing to use. Laquer primer needs a solid surface, such as non flexible metals. NEVER should be used on plastics. Even spot jobs. A flexible polyurethane primer should be used. The laquer can also damage the plastic (melt!) and stop adhering.... causing peeling in time.
Hell, I am in the wrong industry. i should have stuck with paint and body repair. Jeez do I miss it![]()