During sales the site operates with reduced feature set to spare resources.
This could be one of them (...or not).
I think the "bigger" the site the "bigger" the number of attacks against it, so security is probably the first priority, then comes to keep the payment system up and running and pretty much everything else is in the "we will take care of it...at some point" category.
I don't expect this "some point" to be anytime soon....