From our most recent lecture we learned that requesting seller responses and selecting vendors is part of directing and managing project execution. During this phase you are obtaining quotes from approved vendors and verifying them with quality systems depending on the components critical impact to your product. The company has done their due diligence in composing the list of approved vendors, taking into account their track record of success and quality. Ideally an issue with quality of product coming from a vendor shouldn’t happen, but in the real world it is always possible so I think, depending on your time constraints, you should let the vendor correct their manufacturing issue via their own internal root cause analysis and give them a deadline for expedited delivery, if its possible to visit the facility then you should consider it. Maybe even try to get a discount to compensate for lost time, at the threat of losing you as a client and missing out on all of your future production needs. I would think that switching vendors is also a viable option, but depending of the severity of the defects and if the vendor was able to correct them, it is a good idea to work out a deal that makes up for lost time in the form of a discount on future bulk production.