Per the service folks in Scottsdale yesterday, there is a new bulletin, issued "a couple of days ago", that details a procedure to address the creaking. From what I gather, there may have been a problem during the assembly where part of the rear parcel shelf in the corner was installed incorrectly. The remediation involves bending some part of the shelf to the correct orientation (my words, I can't remember exactly how they described it to me) There is also an updated rear deck shelf. Mobile service is coming out next week to try the remediation. They're also bringing the updated shelf to replace if that doesn't work.