It's the wire. On my packs they come out of the corner of the pack. Although the wire is very flexible, it isn't able to make a 90* turn and come up and out of the provided wire notch in the battery box. ONe of the packs will sort of work if you put a lot of pressure on it, but the door is flexing itself to make the catch. Not a good situation. If the wire came out of the middle of the pack, I could cut the fins out of the exit vents and route it up and out of there.

What brand 6000mAH packs are you running? Link?