"Check Redundancy State" is usually part of a longer Navigation Error message. The root cause is the inability to acquire sufficient satellite data.
You can try different locations on different days (outdoors always) to have other satellites available. I've heard a few members fix this with IMU calibration but not sure if they had the same problem you describe.
However that message is most commonly that message is due to a bad GPS board which is best repaired by DJI.