Drag a marker

Hi,
I have a strange problem when i drag a marker.
I hide somes markers ( by setting an empty image in icon url ) and ajaxrender the map without problem but if i drag one of them , all markers are merged at the latest location when i Ajaxrender again ..
see video http://assapan.fr/DragMap.mp4
I have a strange problem when i drag a marker.
I hide somes markers ( by setting an empty image in icon url ) and ajaxrender the map without problem but if i drag one of them , all markers are merged at the latest location when i Ajaxrender again ..
see video http://assapan.fr/DragMap.mp4