This paper examines why well-designed digital technologies in healthcare repeatedly produce clinically fragile systems. Rather than attributing failure to poor implementation, resistance to change, or insufficient training, the analysis identifies recurring system failure modes that arise when healthcare is treated as an optimisable technical domain rather than a complex clinical system. Drawing on systems theory and empirical experience from large-scale healthcare digitalisation, the paper describes how digital systems disrupt clinical flow, externalise cognitive and organisational load, misalign governance, and diffuse professional responsibility. These failure modes recur across electronic health records, decision support tools, registries, scheduling systems, and AI-enabled platforms. As part of the Clinically-Grounded Systems (CGS) series, this paper complements earlier analyses of system emergence, human-centered logistics, and patient-engaged governance by explaining why digital systems predictably fail when these conditions are absent. The paper is intended for clinicians, health system leaders, designers, and policymakers concerned with the safe and sustainable digitalisation of healthcare.