Edge 1030 disconnects from Varia RTL510 in same place on route

OK, this is really weird... I've had my Varia RTL for nearly a year now and it is generally very reliable. I get the occasional "Radar Disconnected" message now and again but it always reconnects in straight away.

What I do find very strange however is that it always disconnects at a point 3km from home on the same road without fail. And when I say "at the same point" I mean within a 10 metre zone. All my routes are different distances and speeds so I can rule those out as culprits. 

Any ideas anyone? Is there likely to be some very localised radio transmitter that interferes with the Bluetooth signal?

Grateful for any suggestion, please.