Connector of antenna (NFC shield v2.0)

I am using NFC shield v2.0 and I find it very convenient the separation of the shield and the antenna.
I have purchased 3 NFC shields and I am running the same Arduino sketch with all of them. Two of them work fine but the behaviour of the third one is quite erratic. Some times it will read a tag, some times it won´t. If I start moving the antenna and the cable, in the end I can get it to read a card, but obviously this is not an acceptable solution other than for testing purposes.
Have you experienced any similar issues? do you have any recommendation about how to place the antenna and the cable?

Hey , maybe you can exchange the antenna between the erratic one and others , whether it is the problem of the board or the antenna.