That's a connection error, If you never opened the Drone or had a crash, I would say you need a new IMU....You can try to reload the firmware BUT If the error just all the sudden appeared for no reason and its not intermittent, I think your ESC...
I've found them more fragile when "trimming" tree branches and in bird strikes. They tend to shatter rather than bend, leading to more prop damage, and a greater likelihood of not being able to recover and still fly back home on lightly damaged...