The increasing specialisation of industrial production is leading to a corresponding increase in the dependence of companies on the quality of supplier parts. If their quality does not meet expected levels, this can result in costly disruptions in the production process. BRP-Rotax GmbH & Co KG motors consist mainly of purchased ready-to-install parts. Further reductions in supplier-related error rates in the company are required due to the switch in assembly from line production to a one-piece flow, where the negative effects of non-conformities can be even greater. In the context of this work, the reduction strategies for non-conformities in die BRP-Rotax GmbH & Co KG supplier parts are demonstrated by applying benchmarking, as well as an error cause analysis. The benchmarking results show that monitoring supplier errors with a focus on the ppm figure is not meaningful enough for a holistic evaluation of performance. For this reason, further key indicators must be used to improve performance in the long term. In addition, the long-term continuation of benchmarking is recommended for a more in-depth comparison. First, an evaluation model for suppliers was developed as part of the error cause analysis, which provides a ranking of suppliers according to the effects of their non-compliant components. Based on the ranking of this evaluation model, the non-conformities of the suppliers with the greatest errors are analysed for the occurrence of the error. Finally, a catalogue of measures was derived on the basis of the findings obtained through benchmarking and the error cause analysis. A key finding is that the impact of non-compliant parts is not reflected accurately enough in the company. In order to achieve an improvement in this point, the assembly line error report has to be integrated into the SAP, because this is the only way to achieve the necessary data integrity in order to accurately represent suppliers' failures. This transparency is necessary in order to be able to introduce key figures that portray the effects of non-conforming supplier parts in the company, especially in assembly, in accordance with the causes. The evaluation model developed in this work represents a starting point for the development of such a system of indicators. Only if the effects of supplier failures on BRP-Rotax GmbH & Co KG are presented clearly – in particular the consequences for a one-piece flow – can future sourcing decisions in the selection of more qualified suppliers be influenced. This can achieve a long-term reduction in disruptions to production operations due to non-compliant supplier parts.