Citroen ZX central locking

[bnwrrn]

Recently my ZX's C/L has been going a bit mad. When unlocking the door from the drivers side, and after a few seconds, the central locking will repeatedly lock and unlock the rear drivers side door and boot, about ten times before stopping in the unlocked position. When locking, the central locking does not work and I need to go around and manually lock the drivers side front and rear doors, and the boot. My battery is a bit flat so that would explain why they wont lock, but I'm not sure why the locks go haywire when unlocking. Has anyone had this problem before? What did you do to fix it?