Research has shown that one type of common procedural error, postcompletion error, occurs systematically under high working memory load. Studying the effects of different interventions on this reproducible and well-explained error type may help extend our understanding of the underlying psychological mechanisms behind human error and interactive task behavior. Experiment 1 was an investigation of the error-reducing efficacy of a simple visual cue and a separate downstream error cost condition. While neither was found to be reliably effective, this inquiry provided valuable insight that led to a follow up study. In Experiment 2, a cue based on design guidelines and a mode indicator were implemented to explore possible reasons for why the previous interventions failed. Only the cue had a reliable effect, demonstrating the difficulty of designing a successful intervention. Finally, a computational model based in ACT-R was developed to provide theoretical demonstration of this finding.