Version "D" (I have one) came with the first generation of quick release props. Reports of props flying off prompted DJI to redesign a 2nd generation of QR props that came with V2. They have a locking device that can easily seen and verified when locked. First generation props, the locking system was underneath the hub and could not be visually verified. Some of the issues were plastic parts that cracked and failed but I believe some were caused by pilots not insuring that they were seated properly. Personally, I have never had an issue with the first generation props. I inspect them regularly and hold the motor hub with one hand and the prop in the other to insure that it is seated properly.