Fastfly, there is a cable connecting the positive terminal of the batt and the glow plug contact. If you unscrew the shaft from the battery compartment, you can see it. I suspect that this cable is electrically open and could explain why it is intermittent i.e. you need to tweak it to get it to work. I suggest that you contact Tower for a replacement then.

Fastfly, may I also know what engine and type of plug you are using ? Did you fit the connector to the plug correctly ? If you post a pic it will help.