I had a fibreglass boat for years. Washed the salt water off after every use but never polished it and never had a problem. It was stored outside in all weather conditions.

I'd be getting some expert advice.

 I have a 2010 Jayco Silverline 2165. The fibreglass iws aas new now as it was when it was new. It has been around the traps a fair bit. Done th half lap a couple of times.

been through all kinds of weather. storms , red dust storms ' W/A ' strong winds and rain on the Nullarbor. 

I cannot fault the van at all. Happy Jayco Owner. Doug

Ive never worked in a caravan manufacturing business, but I have a lot of experience in other fibreglassing.

Cloth print-through on one panel of one van produced means that it is not a mold problem. It is a fault with the manufacturing process. It is caused by the gelcoat for that panel being mixed too vigorously in the pot before spraying commences (air bubbles in the gelcoat), then the gelcoat layer being sprayed on too thinly (didnt stick to proven quantities, didnt follow strict even spraying techniques, didnt use a depth gauge to check and sprayed in poor lighting conditions). Then the tie layer of 225gm csm was rollered down too vigorously into gelcoat which wasnt fully cured with not enough resin and too much catalyst poorly mixed (a hot mix which shrinks and pulls on the gelcoat). They were very lucky to not get gelcoat crazing. They may have even used white pigment in the resin to try and give more depth of colour to the thin gelcoat layer and hide gelcoat crazing. They probably then laid the core material straight down onto the wet resin. If they used a core material like unprimed 4mm mdf board, (which is porous), that would have sucked the gelcoat away from the mold and impressed the cloth fibre into the gelcoat. All these mistakes done together, causes print through and are the result of trying to reduce costs and delays, using inexperienced labour working under too much pressure to produce a panel in hot working conditions with poor lighting. Inadequate factory lighting (and a tight time schedule which doesnt allow examination of the panel off mold before further work is invested in it) can mean that panels like this escape early detection and are less likely to be rejected.

The panel should have been rejected because it will only get worse as the thin porous gel coat breaks down under uv light, dulls off and is abraded away during further vigorous polishing. It has probably already been sanded and vigorously polished in an attempt to reduce the print through effect. If it was a flat panel formed through vacuum bagging, I would say it is a classic example of too much vacuum pressure being applied. The only viable repair option is to key the surface with a 400-600 aluminium oxide paper applied dry, apply two coats of highbuild 2 pack primer, buff flat, and then spray two coats of two pack paint. Your problem there is that it will never look the same as the other panels and age/fade at different rates. I wouldnt have taken delivery of it. The cheapest option, is keep that side polished with white car polish and dont look at it. My 2 cents worth.