I am flying the same receiver and starting out flying my Skygate Hawk using 2 of 3600MAH life batteries. I have about 25 to 30 flights on it with cortex. I check the batteries after every flight. I would swap them out after 2 to 3 flights with freshly charged ones. I am using 8711 all the way around including gear doors. I haven't seen any issues at all yet.

I now use the 4500MAH batteries and can fly up to 5 times before seeing 40% of battery loss. I also fly with telemetry and have alarms on the RX and Turbine voltage. I am sure I could a lot longer but I see no reason to take the chances. I keep batteries charged and ready for every flight.

I not sure what cause your problem and I glad you didn't loose the jet. Please let us know if figure out what happened.