They seem to be struggling with so many different systems, that with their architecture choices, this sort of error kind of makes sense.

They have one system that says offer cheap upgrades if there will be open seats. Then another system that handles upgrades. Well, if that upgrade system is broken, as is currently the case, it makes sense that the upsell system would be basing its decisions off of questionable data, thinking there are seats aplenty to sell.

If you run into a Chicago or Houston Walgreens and they're out of band-aids, at least you'll know why...