Hi I am Rick, UK Plumber, and I specialize on Boiler problems, it is not dangerous, but I will have to look it up to find what it means.
I have four sets of instructions for these and not one of them mentions the alarm have pictures of it but no explanation, I have a link to Drayton via the installer web site I will have a look there shortly.
Well they do not give a lot of info, but reading between the lines it is a "receive error" which means the SCR is not reliably getting the signals from the stat, this could be due to low batteries in the transmitter (stat) although the unit is not flagging low bats yet, the other possibility is the distance/position between the two units bear in mind the max distance stated is under absolute ideal conditions the real effective distance is usually a quarter of that, but replace the batteries first and see how it goes.
OK can you give me the exact model you have (marked on the front of the stat) as there are many variations.
The model is Digistat SCR Wireless.RegardsAudrey
The room stat has batteries in it and at three years they are very low, cannot find any digitalis that are mains powered on the room stat, in fact there would be little point in having wireless if the rooms tat was mains powered as the supply would come from the boiler system anyway, so the wires would be there, so remove the unit cover on the bottom right with a coin.