Never and ever use an extension cable with the multi tap, at least not between the console and the tap. Between the controller and the tap is alright.
The reason is the multitap has to send 5 times(of course depending on the ammount of ports on it, less for less ports) the data than a normal controller. Using a extension cable will degrade the signals five times as much as it normaly does. Which causes problems. Most likely yours is a product of that.