Vector 2 - 4 flashes (not pairing)

Hi, sorry for posting this in the vector 3 area but I don't see anywhere to post about vector 2.

My dual sided vector 2 were working fine during the summer, and had some fresh batteries in at that time. Then over the winter the bike has been on an indoor trainer and using the trainers power data rather than the vectors.

I went for a ride outside yesterday and initially my head unit wouldn't see them; so I figured the batteries were dead (though if that was the case, they died quicker than usual) - so I bought some fresh ones and since then they have been stuck on the "looking for other pedal" 4 flashes.

I used the vector updater utility on the my laptop, it says it can only find the right pedal; even if I take the battery out of the right pedal so only the left has power, it will still say only finds the right (rather than not finding anything or saying it only found the left).

I've also noticed that the Left side never stops flashing (4 times per 10 seconds) while the Right side seems to power down after a while and stops flashing; starting again if I spin the crank.

I've removed the batteries multiple times, I've disconnected the pods and cleaned the contacts etc..

Any ideas?