HR Connectivity mid-ride failures between Garmin Forerunner 35 and Edge 130

Hi all

I have an intermittent issue which doesn't happen on every ride, but when it does happen, its very irritating.

I broadcast HR (heart rate) from my Forerunner 35 to my Edge 130, wait for a stable connection, and then commence my ride.

But somehow, at some point in the ride, not necessarily when it auto-pauses, just randomly, the Edge 130 loses the HR read from the ForeRunner 35... and displays --

I have to stop, stop the broadcast from the Forerunner, restart the broadcast, wait a little while, and then about 80% of the time the Edge starts to receive the broadcast again without me having to stop the ride and start up a new one. On occasion, I have had to completely stop the current ride and start a brand new one.

What could be causing this intermittent failure of HR broadcast between Forerunner 35 and Edge 130? Please assist? Do I need to change a setting? Do I need to switch off bluetooth connectivity with my phone? is that interfering?