Fuel Filter Replacement Problem

[wullaby]

I have a 2003 4.4i with 80K miles, so I thought it would be good time to replace the fuel filter, I ordered a Mahle brand replacement for around 70 bucks. After dropping the huge cover and the fuel lines, I placed the Mahle and plugged in vacuum hose and the FPR and other fuel line, the rear fuel line next to the vacuum line facing outboard to the vehicle would not "Snap" in place like the other two. My buddy was with me and he suggested to get a bmw oem fuel filter, so he drove me up and we paid 130 with tax and came back, once again the same rear fuel line feed connector would not snap on. So I took it off and put the Old original fuel filter and it snapped on with no problems. Since it wouldn't snap with the other two, I didn't want to risk driving and having my line fall off and spray fuel and possible fire! Anybody know what I am doing wrong? The part number on mine and the OEM BMW one I bought were exact same, and I told the parts guy and he refunded me the money. I asked the SA and tech and they said they had no clue......thanks in advance for anyone who has experienced this.