...three flight controllers ... two different sets of sensors ... independently compute the desired actions to take, and vote on what to do. Each ... has its own power source, backup battery, networking hardware, and set of critical sensors.
You didn't mention activators. Do all the redundant components you mentioned connect to a single voting system, and single set of actuators? How do you avoid your voting system and actuators being another single point of failure?
Or does each redundant system have it's own set of actuators, and enough of them to tolerate failure of one set? (e.g. three sets sized such that two working ones can overpower one erroneous one)