If any requirement in the Design Verification (DV) Protocol is not met during testing you will be unable to complete DV until this situation is rectified. I have been in this situation before and there are a few common options you have to choose from depending on specific requirement that was not met. Like it has already been mentioned one possible way would be to re-look and re-evaluate the actual requirement that is not being met. There is a chance that the requirement was originally made was too conservative and changing the requirement to something that can be met could be easily rationalized. If you cannot change the requirement another option could be to test more samples. For instance if it is an attribute requirement and the acceptance level is test N=120 samples with 0 failures, you could check to see how many samples you need to test to in order to accept 1 failure which may be N=250. Testing additional samples would require a deviation but is a lot less paperwork and time then changing a requirement. Another option could be to rationalize the failure that has occurred through engineering logic and evaluation. This option tends be more difficult because it requires a deep understanding as to why the failure occurred and why it will not impact product that will eventually be sold to customers. An example of something like this could be a sample that failed due to manufacturing defect and it clear that the failure was caused by the manufacturing process, and there has already been a fix put into the manufacturing line to correct this problem. This does require a lot of documentation but the failure could be rationalized and no additional testing or requirement change would be needed. These are some of the common examples that I have used in the past, but in really depends on the each specific situation what the best route to address the failure in DV. My only advice would be to not always assume a major change is needed, make sure you have a full / clear understanding of the problem before deciding the best way to address it.