My newish HRM 200 suddenly stopped broadcasting in ANT+

It connects fine to Garmin Connect Mobile and shows firmware 5.10 . Not sure when that was updated. Tested with various apps on the phone and they get heart rate fine from Bluetooth.

On my Grmin Epix Gen 2 and Edge 1040 it was perviously paired using ANT+ connection, but since yesterday it won't find the connection. I had to remove the paired sensor in both and Add New Sensor now shows only Bluetooth as an option. Once paired using that it connects fine and heart rate starts showing up. 

So two questions:

1. why would ANT+ already paired suddenly disappear?
2. I had always thought ANT+ is better since unlimited number of connections, is there any reason top prefer Bluetooth (if you have the choice)
3. Is removal of ANT+ intentional on Garmin's part/

Thanks.