I really hate it when someone comes in to raise new issues after there has been protracted negotiations, or things are supposed to be close to final. Worse still, these are often people who are either higher up, or gatekeeper departments. They are either so swamped they only come in at the last moment, feel they are so high up that it is beneath them to get involved early, or simply happened to be curious.

Things could be better, I know. Most projects are not executed perfectly. But, if you want to weigh in, then you should do so early, so that your views can be taken in at the right time. Timing is everything. Sometimes it can't be helped, if you spot something critical at the 11th hour, it has to be changed. It doesn't absolve the fact that it could have been handled much earlier on.

The last minute scramble is inefficient. It wastes all the work done earlier. Quality falls as quick fixes are applied to solve the problem. It makes everyone else look bad.

As a project matures, every amendment must be viewed together with the cost of executing the amendment. That cost increases the later it gets. If you want to change something, it had better be worth it. Otherwise, let's be willing to live with some imperfection. 

What if the very problem raises its head, who is responsible? I hate blame culture anyway. But it should be the responsibility of the one who raised the issue late. It means they needed a process or better thought to have caught it earlier.