HRM pro + Having to reverse polarity to get it to work

My HRM has recently developed a weird bit of behaviour. It only starts after I reverse battery polarity by removing and replacing. It then stays connected until I remove the HRM from my chest. When next I come to use it the same problem and the same solution. I have tried Garmin support but they were unhelpful. Anyone have any idea what could cause this and is there any fix or is it just fit for landfill after less than a year of use. I have tried replacing battery, three times, washed strap and all the other usual solutions. 
I’ve had Garmin HRM’s in the past and swore never again, made the mistake because this was on sale..Wish I’d got a PolarGrinning