This past spring, when I got my first ball lock system, I had a couple problems too.
First, despite the lines coming "pre-assembled" the MFL connectors were were tight, but not really tightened.
Second, the gas lines did not have nylon washers. (The kit included them, but they were not in place.)
Third, I did not realize about pulling up the ring when pushing down the connector, so connections were nearly impossible to make.
When I finally got my lines connected, the MFLs squirted and hissed. I even broke a gas connector. I was like, "Oh sh*t, what have I dropped all this money on?!"
Luckily that first keg was just filled with water to test the system. Once I learned, I haven't had trouble since.