It seems the company has a lot to worry about and updating the Gantt Chart may be the last of their worries. The balloon pops immediately instead of lasting for days could be a catastrophic issue and could result in termination of a program if the problem is not resolved. Unfortunately the link provided at the starting post is no longer working so I could not read about the details. Assuming the issues happened at design verification, I agree with others that all of testing might have to be redone. However the first thing the engineering group would need to do is identify the root cause of the problem. This would require research, testing and evaluating. Maybe the test method was not followed adequately (e.g. certain steps were not followed or performed incorrectly) which resulted in failure, or the unit was not stored/ handled adequately prior to the test, or a subcomponent failed which resulted in popping the balloon, etc. There could be many things that could have happened to cause the failure and hopefully is not a design flaw that requires going back to sketch board/ concept phase. Once the root cause is identified, the engineering team would identify solution(s) to the issue and then the PM could re-assess the Gantt Chart based on the solution that the company pursue.