Understanding measurement uncertainty is crucial in experimental physics, as it enables accurate and reliable measurements, facilitates comparison between measurements, and aids in designing experiments. Consequently, measurement uncertainty has emerged as a critical learning goal for many introductory physics labs. Here, we explore the impact of a recently transformed introductory physics lab at the University of Colorado Boulder on student understanding and interpretation of measurement uncertainty. The transformed course was explicitly designed to prioritize understanding measurement uncertainties as a learning goal and replaced verification labs with measurements where students could not predict the outcomes in advance. We used the physics measurement questionnaire to assess changes in student reasoning about measurement uncertainty at the beginning and end of the semester. Using a subparadigm coding scheme, we assessed different types of prevalent student reasoning and observed for trends in reasoning surrounding measurement uncertainty from the beginning to end of the lab course. Clustering algorithms were utilized to categorize student reasoning and compare these pre- and postsurvey responses. This analysis offers valuable insights into students' reasoning about measurement uncertainty, including the diversity of initial reasoning clusters and the narrowing of reasoning elements into primarily more expertlike responses after the transformed course. However, challenges were observed in transitioning students from certain clusters, especially those that exhibited brevity in their presurvey responses. Overall, the findings reveal the potential for targeted interventions to deepen these students' understanding of measurement uncertainty in experimental physics and underscore the significance of evidence-based instructional strategies in physics labs for improving student learning outcomes.