As I noted on Bluesky:

I'm used to people not keeping their software promises (though I think mis-estimation of release dates is a Very Junior thing to do in software dev, and means you have not fully absorbed the lesson of It Always Takes Twice As Long As You Think It Will). But to have a piece of software slip by nearly a month, and then to be told that the reason it's still slipping is because you found a problem with the structure of the underlying data which I warned you was a problem when this project was still a gleam in everyone's eye, and which I have been telling everyone was a problem for many months, is just unacceptable.

I have literally been blowing this horn from the beginning. No one has listened. At one point I was flat-out told I was wrong (in a rather large meeting, which was mildly humiliating). At other points I have been given all sorts of vague assurances ranging from "won't be a problem" to "we'll work around that" to "we can handle that by adjusting process" (read: It'll require hand data entry, but we'll have the ability).

They didn't just say today "We're late because of this." No. They said they were late because they had just discovered this and they were going to need to restructure the work for it.

If you come to bring a piano into my home, and I warn you that the floor won't hold the weight of one right there, and you ignore me and put the piano there and it falls through the floor, that is your problem and your fault and I laugh at you and make you fix the floor and do it right.

If, however, you try to tell me that now the job will take another month and will cost me more than I originally paid you, you have just tried to make your incompetence my problem, and I will have to take action appropriately. No, sir. I warned you and you did something you could have avoided if you'd just listened. That ain't my problem and it ain't my bill.

These developers have not quite done that -- yet. But I sense that they are gearing up to, and I am taking preparatory measures.