As mentioned in the direct conversation:
I don't know your consumer rights but over here this would be a clear case. Dead after a few days would qualify for immediate replacement at the shop. I would try to not use DJI warranty, as this would take some time and you never know what they are going to make out of this.
Whatever you do don't open it, this would void the warranty. Just return it, this isn't your problem but the shop's problem