Dear Paul,
I had a similar problem on my Gib Sea.If your fridge has a keel cooler type anode,it would be worth checking the bolts and associated backing etc.for corrosion.
If you fridge has a drain cock at the bottom is it closed?
Finally,I over filled my aft tank and the breather hose was blocked,the overflow leaked from the inspection cover ( I had not tightened it correctly).I was convinced I had a leak,as the pump kept pulsing.The water lodged in every stringer and found its way into the strum box. It took ages to trace it.
I hope this helps.
Derek