Late Delivery defect unable to remove

[oceanartsnorthdevon]

Not sure if I am posting this on correct board but as a business seller I have had an item marked late and this has come up as a defect on my seller level now item in question was sold late in the evening on Friday 3rd July and on listing it was down that I would get item out in 1 day. It was a heavy item and courier collected the Monday 6th July so from my end I done what I said on listing.  Courier is a 5 working day despatch from collection and was delivered on time and tracking is on listing for ebay to see, now buyer is saying item was late?  I have disputed this saying to check tracking as it clearly shows item was collected and delivered in stated time.  Ebay's response is they won't remove defect and I cannot appeal it?  I am puzzled I have done everything that I should have done but have a defect as buyer says item was late even though tracking shows it wasn't? How is it my fault, in fact considering the way things are due to Covid I am impressed it was delivered on time as there are still delays in many areas.

[arkwebus]

Sadly many of the responses from ebay are rather automatic.  The nuance of what you are saying may not get through.  I doubt there's any more you can do

If you promise next day despatch then many couriers work 7 days a week including Saturday and Sunday [which is where they score over Royal Mail?].  

The days of Monday to Friday 9 to 5 working are gone.  Whether that's good or not?

@oceanartsnorthdevon