Crossfire failed me :(

Had a great day flying until some how, out of the blue, in an area we had flown plenty of times I get a dead duck failsafe into the ocean. Running a diamond antenna with horizontal polarisation and an immortal T on the quad. At first I thought it was a connection issue with the crsf receiver but now I'm not so sure. Any help would be great cos I really don't want this to happen again!