ebay refused to remove my late delivery defect despite tracking shows delivered on time

[gx_autosport]

Hi there, 

Ebay's new defect system seems to be a pain to deal with, since ebay switched out to deal with defect digitally through their system, they have never actually removed any defect for us. 

The latest one is causing a lot of frustrations, the buyer left us a feedback and selected that it was delivered late when it wasn't. We uploaded tracking to back this up on the portfolio, received an email from ebay saying the following:

----

We've reviewed your request to remove the late shipment rating related to this transaction. 

We cannot remove it in this instance, as it is an indicator of a less than positive buying experience. We understand you may feel that you did everything to take care of your buyer.

Please note that this decision is final and cannot be changed or escalated.

----

Spoke with an operator Sandeep on live chat who just repeated and repeated saying nothing he can do then disconnected me on live chat. 

Could anyone suggest why ebay would not remove the late delivery defect despite the tracking shows delivered on time?