Constant Battery Drain

I’d had a few Missing Right Sensor Issues which I sorted by cleaning all the contacts with Alcohol.  I then put in a brand new set of Duracell Dl1/3N batteries.  1 week later and the pedals wouldn’t wake up at all.  Removed the batteries and checked them with a multi-meter and they were both below 2V.

I put in another set (not brand new) yesterday and recorded the left and right voltages of 3.02 and 3.08V.  24 hrs later (bike not ridden) I removed the batteries and checked the voltage again - 2.13 and 2.66V.

So something is badly wrong!  

Any ideas??  A pair of batteries a day is going to work out very expensive!