Cracks Developing in Fiberglass

From what you are describing it sounds like an area that has a gel ooat thicker than .020 ins. Resin expands at a much higher rate than the FG underneath and hair line cracks develop. This usually happens in the radius of caps or recessed areas where resin pools. Is this in a full body paint area? Dark paint can make this worst especially in a state like Az where temps can reach 100 plus. What year an model is your MH ? Some years use used resins that made this problem worst.