I don't know if anyone watched the video until the end, but it appears as though DJI determined it was some kind of defect as they are replacing the drone for free.
There are times when DJI(and many other product manufacturers)will supply replacement product not because of a faulty item, but simply to keep a customer happy. AKA “good will”.
There are times when DJI(and many other product manufacturers)will supply replacement product not because of a faulty item, but simply to keep a customer happy. AKA “good will”.
Or they want to avoid the bad press of a disgruntled YouTube personality.
If they have a bad batch of propellers, it would make sense to out in front of the issue. Assuming that was the case. It could also be a problem with a batch run of motors.