Sometimes documentation doesn’t help. My workplace used to be waterfall and we still have systems analysts producing documentation

One piece of work came to my team as “this calculation fails in this case and we can’t tell why”

Looking at it there were two updates in the documentation showing updates ten years ago the first fixing that corner case with the second fixing a side effect of the fix

Why didn’t it work? It was never built, or perhaps built but never merged

On the good side we have an excellent plan for how to fix that corner case, on the bad side we aren’t funded to do that amount of work so we have to half arse a solution