This study presents a comprehensive evaluation of an open-source Level 4 autonomous driving system through extensive field testing across 236 km of mixed traffic scenarios. The research utilizes an Autoware-based software stack and classifies 30 disengagement events using a novel five-level criticality framework, revealing a spatial disengagement rate of 0.127 per kilometer. Analysis demonstrates that perception and planning failures account for 40% and 26.7% of disengagements respectively, with object-tracking losses and operational deadlocks from parked vehicles being primary failure modes. The findings highlight critical challenges in computer vision-based perception and tracking systems for autonomous vehicles operating in complex urban environments.