Thanks for your replies Dan. I take your point about the the equipment next to the controller. It's actually a redundant CD player which hasn't been plugged in for years, so no electrical interference, although maybe some magnetic interference which could affect comms.
However comms is not the problem. The binding process between two wireless devices is a 'once only' exchange of data and once bound, a device should in theory store that for life, even if powered off. It's like pairing two Bluetooth phones together. Once paired, they can be 100 miles apart. They won't communicate, but will always be paired. The problem in my case is that the BDR is losing its binding data, so won't talk to the controller.
As you said, it's probably the BDR which is developing a fault. Maybe a software/firmware glitch. I was hoping someone else may have experienced this problem and resolved it. At the moment it's a very infrequent fault which has I think happened three times over the past couple of months. However it gets worse, then I guess a replacement BDR may be the answer. Interestingly the controller is bound to nine other devices and none of these have lost their binding.
Moving the controller is an easy option, although it's been in that location for over two years without problems. I'll give this a try and report back, but due to the infrequency of the fault it may be some time.
