Shipping Rates Intermittently Missing From Order


This is more of a "Have you experienced this so that I know I am not going mad" type question, rather than anything I expect to find an answer to.

We are intermittently finding orders that are missing a shipping postcode, even though the user has enter a valid postcode and matches a shipping location with rates in our backend.

I have even watched replays of their checkout process on and noticed that they are being displayed a shipping rate on the checkout, which means that the backend has stored their postcode in the user_data session variable.

But for some reason when they get to the checkout page, the shipping rate is no longer applied.

I can't determine any particular pattern as to why this is happening, it doesn't appear to be linked to any particular payment method or any particular postcode or browser version.

Anyone else experienced this?!


I should also add that their postcode is appearing in the order information, so it is not like the session data has been deleted anywhere along the way in our checkout process...

I should also add that if I edit the order, I can see the shipping rate for the order, but it is not selected to be applied to the order (the plot thickens).... I think this is purely because when you edit an order, it recalculates everything. So maybe no great suprises here.