It could be the connection for the coil, where it plugs into the main housing. I had read that dirt and gunk can get inside the socket and cause it to behave erratically. What you can do is unplug the coil and make sure there's no dirt or anything in the plug housing. On the control box, there's two screws that hold these two pieces of a plastic "bracket" (for lack of a better term) that holds the socket in place. Remove those, and you can pull out the socket. If it was anything like mine on my Pioneer 202, you'll have dirt and dust caked in between the metal contacts. Clean that, and plug the coil back into the socket before putting the brackets back in place, as they help keep the plug plugged in snuggly, and you have to move it around a bit to ensure a tight connection between the two. It'll make sense when you're looking at everything.
While mine wasn't as bad as yours, doing that certainly made a big difference. That, and also making sure the cable is wrapped so that there's no slack that can wiggle while you're swinging the coil back and forth, since that can apparently cause false beeps. That, and also make sure you're using good quality alkaline batteries, that don't say "heavy duty" on them, as those can affect performance.
Good luck.