A few questions:
- What are you running? If you are running the air/con along with electric hot water heater (or similar high draw devices), you are probably overloading the plug.
- Was it at the same campground or more importantly the same site?
- At home what are you running? If it's just the fridge, it's highly unlikely to be the issue as that is a draw of at most 2 amps...well below what a 15/20amp outlet can provide.
There is the off chance that you just got two faulty cords but I'm betting you are running too much power as the most likely. As others have mentioned, far cheaper to replace the end rather than the whole cord.