One-dimensional ground-based monitoring tools are widely employed in open-pit slope stability assessment due to their affordability and relatively good accuracy. These tools offer effective temporal accuracy within 12 to 24-hour intervals per data collection, satisfying the monitoring needs of geotechnical departments and general management. However, the case examined in this paper reveals the potential limitations of these tools. Despite daily conditions showing scatterer movement detected by seven installed monitoring tools, interpreted as noise attributed to atmospheric factors, field inspections uncovered signs of slope instability in the form of multi-bench cracks occurring beyond the monitoring range of the one-dimensional tools. This discrepancy was further re-evaluated by back analysis results indicating critical values of Safety Factor (SF) (1.0 < SF < 1.1) under seismic loading from blasting at 0.04. The paper examines the use of Terrestrial Laser Scanning (TLS) for daily spatial-temporal monitoring, revealing slope geometry changes in areas with cracks and minor landslides during two days of peak instability. This method addresses the limitations of one-dimensional ground-based tools by providing high-resolution data for a comprehensive understanding of slope stability and early detection of instability indicators. The case study highlights the need to complement traditional methods with TLS-based monitoring to improve the detection and mitigation of slope instability risks, advocating for more comprehensive strategies to enhance the safety and sustainability of open-pit mining operations.