Missing a milestone is not bad at once; however, missing more than 2 milestones lead to significant reductions in customer satisfaction and confidence which is bad for company’s reputation. It could be avoid by examining key possibilities in detail that can get to the root cause of the problem and get the project team back on track toward on time delivery of critical project tasks. I agree with some of the above posts quality matters. We don’t want to finish the project that cause any problems later on. Also, you should know from your clients’ perspectives sometime they value time as compared to cost and quality.