My Boss therm BR1 receiver works erratically?

My new Boss thermostat controls work erratically. Normally the BR1 receiver shows a green light at the top ( I think that indicates it is connecting to the sender unit in the hall) but occasionally it shows red - consequently the boiler won't light although everything is calling for heat. I have to turn the hall stat to about 25c and the back down to to say 12 and finally up again to my required setting of 20, at which point the receiver changes to green and the boiler fires up.