There seems to be a pretty good thread already started on this subject Bluetooth dropping during ride, won't reconnect without quitting, I myself have been experiencing this for a while now, what works for me is I turn off my iphone wifi and bluetooth basically airplane mode and just have the trainer H3 and ATV 4K connected along with the Wahoo Ticr HR monitor that seems to work the best for me did a 2 hour ride on Sunday no issues hopefully somebody fixes this soon.