ANT+ Sensors Dropping Out

Can you see if those drops happen at the same time on all sensors? If yes, then I'd suspect a hardware issue in the watch, in which case contact Garmin support for a warrantee replacement

Interesting to hear this as I've had the same issues recently, but on my Edge 530. Haven't yet had the same on my F965, but then I don't often have other sensors connected to that device. 

For example, on a ride I'll see all sensors drop out for a few seconds then reconnect themselves. This behaviour repeats several times but at random intervals, then can be stable for ages. Does suggest a hardware issue and will be getting back on to Support again (previously was just advised to disconnect and reconnect all sensors, which didn't make much difference).

The only other thing that changed was that I replaced my HRMPro+ with a HRM 600 - that's when the problems started! All other sensors are the same, new batteries/charged etc. 

If multiple sensors drop and come back at the same time, then it sounds like a hardware issue in the watch/edge