Problem solved with a 1.0.0 version of acf gallery field find on a github repository (and acf 4.1.4). I don’t know if it’s an original or modified version but it works fine !
Do you have a repository where we can find all versions archives ?
I found your Github repository but no gallery field on it.
Anyway, good job with your ACF plugin, very clean and professional look and feel ! 🙂