My Standard was driven hard with no issues for the first few flights. Reading here about the cracking issues, I settled down on the hard braking and turns. I inspected the bird religiously after each outing and thought I was immune to the issue. However, when I hit the 20 hour flight time mark, I noticed (to my horror), small cracks under the motor were developing on the silver prop arms. One small crack also on the screw hole joining the two shell halves as well.
I backed off the screws. The silver mounts were particularly tight, crazy tight. I also supported the interior mount areas and screw areas with Bondic, on all arms. After the repair, I flew for two more hours. Gentle. More cracks are starting - at least one. This time on the same arm at the other screw holding the shells together. Did I just move the stress to another part of the frame?
I have the Strong Arms on order along with a prop balancer. I used the same set of props from the start but maybe there is some vibration set up and taking a toll on the frame. No crashes or hard landings, ever. Even after all the preventative action in place, I can't help but thinking a new shell is the next step.
Stats are now at 23.5 hours, 283 miles, 137 flights. Only mod is the DBS antenna on the controller (and I'm very satisfied BTW.)
My theory is 1) Mounting screws are too tight and result in damaging the integrity of the plastic. 2) Other factors including prop balance and flight stresses further weaken the shell. Perhaps microscopic cracks created by the over tightened screws develop further. 3) A certain fraction of the shells may not be made to the standard DJI requested and QC isn't catching the bad batches. Who knows for sure what factors combine for a failure to happen. I sure don't. I'm not an engineer or pretend to be. All I know for sure is that the issue is a real one and it's not from abuse. Perhaps Meta4 has said it best....
I hope more of you can post your repair results and share theories.
Update: My StrongArm supports came in yesterday and were promptly installed. Two flights and no additional cracking and the previously repaired cracks held firm. I did order the extra frame as well (2 to 4 week back order).