Just yesterday, I got to my bike after work and noticed the smell of gas. I hadn't done anything to it lately, so there was no reason for the QDs (I think mine are the same as what you were using) to have been disconnected. But sure enough, there was a steady drip drip drip of fuel from the return line disconnect. It was secure, the parts did not pull away by hand and the hardware seemed intact. I broke the connection and re-made it, that stopped the drip. I've got some spare o-rings in my workspace, the next time I'm there, I'll be putting them in.
If you're all about the destination, take a fucking flight. - Frank Turner
Got brap, and twice as much fuel as you. - Akarob