How the bill arrives, and why nobody can attribute it
When it finally shows up there is no single change to point at, and that follows from how it accumulated.
It arrives as a class of problems rather than an incident, and the thing that makes it recognizable is what is missing from the investigation: there is no single change to point at.
That follows from the mechanism rather than being a separate observation. The remainder merged into what came after it, so by the time something fails, the failure rests on a long series of pieces each of which was individually plausible. There is no faulty change because there was no change — there was an accumulation.
| what an investigation expects | what it finds here |
|---|---|
| a change that introduced it | many changes, none of them wrong on its own |
| somebody who decided this behavior | nobody. The behavior was inherited from something nobody examined |
| a record of what it was supposed to do | nothing, because nobody specified it — it emerged |
| a fix that prevents recurrence | a fix for this instance, and no way to know how many others exist |
The last row is why this is expensive rather than merely annoying. You can fix the instance. You have no way to estimate how many more there are, because the quantity you would need for that estimate is the remainder, and nothing measures it.
Do not expect this to be written up as what it is. A review that finds many small plausible contributions and no single cause will conclude that the system is complex and recommend more care. That is a reasonable conclusion from the evidence in front of it, and it is the wrong one, and nobody in the room has the number that would show why.