Checking performed by workers is crucial if safety is to be effectively managed in high-risk settings. We aimed to examine the influence of working memory capacity, mindfulness, sleep, and interruptions on checking performance for the detection of errors. A total of 86 participants completed a 32-min rail control simulation. Participants performed checks that involved matching versus critical analysis and assimilation with interruptions occurring during the task. Higher working memory capacity was associated with higher response accuracy and faster response latency. Response accuracy was also higher when participants engaged in matching compared to critical analysis and assimilation. Mindfulness and interruptions were not associated with performance. These results raise important questions about how checking and error detection can be optimised given differences in performance due to individual characteristics and task requirements.