It's also possible that all the fixes for this were declined by management in the interest of time. If you have a system you can quickly patch suboptimally to get the larger fire lowered, I can see the decision being made to do so. That's clearly irresponsible on management if that choice was made, considering the problem they were dealing with at the time, but if the decision is between "not finishing" and "these few systems still have bugs", I can rationalize it.