So tonight I'm out flying my usual flight pattern and suddenly my controler starts beeping. Every thing looks normal. I'm up about 350ft 400 feet out clear sky no birds , 25 sats. everything is like it always is except my controller starts beeping I rotate drone left and right and beeping starts and stops . Any ideas whats going on. Like I fly this same route almost every night and this is the first time I get this beeping.