SLA is a must to ensure consistency of performance. Also, constant and regular follow up also helps. Moreover, only vendors with good track record should be on boarded

Vendors and partners function as an extended team, and their performance directly affects ours. I manage these relationships similarly to how I would with employees, as- 1. Conducting due diligence before selecting a vendor 2. Performing ref checks 3. Defining outcome-focused SLAs that clearly outline both their responsibilities and any shared responsibilities 4. Holding monthly reviews with action plans to consistently improve quality 5. Providing feedback and engaging in early discussions to facilitate proactive planning 6. Embracing an iterative and collaborative approach to execution 7. Aligning remuneration with goal achievement and quality standards 8. Celebrating successes and fostering a positive, supportive partnership

An SLA, regular progress meetings, monitoring KPIs are no doubt must. Segmentation of the supplier as to how often we buy from them, how critical the materials we receive are also important. So that we can check sourcing alternatives and push vendor integration initiates when necessary

Operational metrics aside , You need to do a broader RCA on your own what is the actual vendor issue that is preventing them to perform management depth, lack of experience on the process /platform , ability to attract or retain right talent Ensure there mitigation plan developed with the vendor for each of those You also need to have internal vendor efficacy grid with some of these criteria mentioned above , with a clear baseline , below which, time to change the vendor and put your exit process in place ( assuming you have build your continuity and contigency plans ) Also have warning threshold baked in your internal SOP like the operational metrics - where you give them the final warning before your exit process starts

Honestly, this is no easy task! Policies and processes aside, communication is the only key to their door! Need to work on a solid relationship with the individual/ team! Other than this having a strong escalation processes should be helpful to an extent! Rest of them are just for the books and brings no result or change!