I also had my first Cold Case radiator leak after 6 months on my LS swap. It was leaking where the fins attach to the right side tank. I have mine set up with traditional coolant and an overflow tank. Coolant level in the overflow goes up/down as it should, so I'm pretty confident my cap is working fine. As with your situation, Cold Case sent me a no hassle replacement radiator. I feel like this may be more of a manufacture defect than combustion pressure in the cooling system.
