First, I am curious if you sent the item to Suunto outside of the US, to Suunto inside the US, or to an Authorized Service Center in the US that is NOT actually Suunto owned and managed.
Also, I noticed one significant item of note in your description of the history of your D9. While your original purchase was made in the US, it was replaced at some point by Suunto outside of the US. I know that the US operation has complete records for each serial number that was shipped to the US and distributed to US retailers for sale. But yours would NOT be on that US shipped serial number list. No idea how detailed those other worldwide corporate records are to tell the story of the pedigree on your problem unit.
But if you haven't already, be sure to communicate that distinction to them - that the serial number you own is no longer the serial number that was originally purchased in the US. That might help them to access a different set of records, or to see your case in a different light. Better yet is if you have documentation for that other warranty replacement.
Also, I noticed one significant item of note in your description of the history of your D9. While your original purchase was made in the US, it was replaced at some point by Suunto outside of the US. I know that the US operation has complete records for each serial number that was shipped to the US and distributed to US retailers for sale. But yours would NOT be on that US shipped serial number list. No idea how detailed those other worldwide corporate records are to tell the story of the pedigree on your problem unit.
But if you haven't already, be sure to communicate that distinction to them - that the serial number you own is no longer the serial number that was originally purchased in the US. That might help them to access a different set of records, or to see your case in a different light. Better yet is if you have documentation for that other warranty replacement.