I just got my drone  back from DJI today. I was sent a customer survey and asked for my opinion of  the service. here is my response

"I noticed a different serial number  from the phantom 4 I sent in from the drone that is being sent back to me. Is  this a new unit being sent to me or someone else's unit (wrecked) that has been  repaired and called refurbished and dumped on me? I do not understand why I get  an invoice with a detailed parts replacement list which I paid for to have  repaired and was told by customer service i would be receiving my original drone  repaired then get a different drone back.
I started this process on April  23rd 2017. I did not get my drone back until today may 26th 2017. This is  excessive "repair time" for not repairing my drone and instead just sending me a  different drone. There was no testing done as my controller was not even paired  with the replacement drone. on top of this I sent in a perfectly good battery  and received back my battery with a crack in it. The battery (sent back to me)  also was installed in the replacement drone. I sent the original battery in to  DJI" not" installed in the drone but in the storage area in the original DJI  box. This indicates poor quality control. I am very dissatisfied with this whole  process as I feel deceived by every customer service rep I talked to from DJI.  First I was told the process would be 10 days from door to door. then when I  called on the 18th of May I was told my drone would be arriving either on Monday  22 of may or no later than Tuesday may 23rd. it did not arrive until today May  26th despite paying for expedited shipping. Please explain to me why your  customer service systematically deceives its customers. If this is how you treat  your customers I will be looking elsewhere for my next drone."

Thank you very much for bringing this to our attention, apologize for the delay in the whole repair process. We're aware of this and working very hard to expedite the process recently.
The replacement products or parts may not be new, for details, please visit: http://www.dji.com/service/policy.
Please leave me your case number since you have doubts on it, I will look into it with the designated team then make it clear to you.
The battery is your original one, but there is a crack now? Could you please upload a picture here at your most convenience? Thanks.
Just to verify, how about the performance after you link aircraft to remote manually?
Truly appreciate your feedback, I've forwarded it to our support team and repair team. We are concerned much about customer satisfaction, and always working to provide you more professional service.