On Board Gas Tank Fumes

I have had a WW with on board gas tank for about 7 years now ann just recently noticed the smell of gas in my trailer after driving down the road. I have the cover off the fill tube inside the trailer and can see no cracks or tears in the fuel and vent line. No obvious damage on the exterior hoses either. The clamp for the fill is level with the floor so getting in to tighten that clamp is nearly impossible. Any ideas to the smell of gas in my trailer?
I do travel with the reefer going but I don't get the feel that it's propane I smell.