It is necessary to conduct an in-depth analysis of the reasons for insufficient quality, identifying weak points in the production process. Next is the development of corrective measures aimed at eliminating identified problem areas. Establish clear acceptance criteria and control points during the work process, which will allow you to quickly identify and correct deviations from requirements. The key is to establish transparent communication with the contractor to ensure a clear understanding of the client's requirements and expectations. For effective quality management, it is necessary to regularly conduct audits of processes and results, which will ensure continuous monitoring and improvement of production performance.

That’s a very broad question but the simple answer is that the QA Manager needs to work collaboratively to put in place processes, training, and tools to develop quality products. The brute force approach would be to become an “enforcer” and put in place a lot of people to find defects and that approach is not necessarily the most effective approach. A better approach is to eliminate defects at the source. Here’s an article on that:

Find root cause for failure and inform to improve quality as per requirement and if he is unable to deliver expected results then has to undergo in depth analysis to come to desired outcome.

Identification and acknowledgment of shortcomings are the initial steps towards progress. Maintaining quality is a continuous process and monitoring should be clear and objectives should be clearly define to smooth the process. The best way to do it is to do continuous SWOT analysis and RCA for the identified shortcomings.

Timely communication and feedback Notify subcontractors of any quality issues with their work as soon as possible and require them to take immediate measures to rectify them. Maintain close communication and understand the progress of rectification.

In my experience, timely and effective communication is of paramount importance when evaluating a subcontractor's work. A way that I've seen works is making them see how their work product affects stakeholders downstream. Making them understand how errors can create bottlenecks downstream makes them aware of their work product. Additionally, fostering a culture of doing it right rather than doing it quickly and communicating that effectively can turnaround a subcontractor's work product

Strict inspection and acceptance Conduct a comprehensive and strict inspection and acceptance of the work provided by subcontractors. In response to the issues that have arisen, subcontractors are required to complete the rectification within a specified period of time. If the rectification still fails to meet the standards, we will resolutely refuse acceptance and request the subcontractor to provide qualified products again.

Open communication is the key. Clearly state the problem to overcome them. You need to have people on same page to bring the change you are expecting. Clearly define your objectives and strategise your move accordingly for better results