Amazon is not calculating the promised delivery dates for premium shipping correctly. Our only premium service is FedEx 2Day. The issue is for orders taht ship on Thursdays (or Wednesday when Thursday is a holiday).

The promise by Amazon is they will use our selected service to accurately determine the delivery date. THat's not happening. FedEx 2Day delivers to many locations on Saturday, but some locations they don't do that. FedEx has an API to check this, Amazon isn't using the API, they just hard code everything to saturday. Every order we receive to a location that does not have saturday delivery, which arrives on time by FedEx 2 day standards counts as late in our Premium Shipping On Time delivery rate

The problem seems to be the "fix" for this issue was done incorrectly:

https://sellercentral.amazon.com/seller-forums/discussions/t/419901aa-26a9-4a18-84da-9ed87493ace2

Instead of using the API to do this correctly, it looks like the fix was to just hard code everything to saturday delivery. We've already lost premium shipping once this year because of this issue and are barely above the threshold again because of this issue. I opened a case, the case gets close with a canned response by someone who doesn't bother to read the words I wrote or look at the orders I referenced.

I reopened the case, carefully explained the issue again, I got the same canned response followed by "please do not open this case again".

This is the promise:

This isn't being done, this needs to be fixed.