Objective: to compare the reasons underlying unplanned ongoing uncoupling repairs (OUR) in order to find trends in component failure depending on the operating intensity. Methods: statistical analysis on the implementation of OUR for two groups of railway cars, classified as “moderate” (up to 600,000 km and/or 3 years) and “intensive” (regardless of mileage, upon reaching 2 years) was conducted. Pareto diagramme analysis was used to identify the principal malfunctions, accompanied by calculations of specific failure frequencies and the failure intensity coefficient. Results: the findings showed that vehicles subjected to intensive use require unscheduled repairs, on average, 1.6 times more frequently per vehicle than those under moderate use. The predominant defect sources were wheelset surface damage, including shelling, circumferential welds, and uniform wear, and the requirement for technological oil replacement in the gearbox. The study demonstrates that both the character and frequency of failures are substantially influenced by operating conditions. Practical significance: the data obtained will help rolling stock owners and operators predict the need for spare parts and production resources required for MRS repairs, optimize repair logistics and anticipate the demand for production resources and spare components for OUR repairs. The research proposes developing a specialized system to monitor the emergence and development of operational defects on the wheelset’s surface, optimize technological processes, and install onboard diagnostic equipment that will facilitate a transition to condition-based maintenance easier.