Failure analysis (FA) and accelerated testing are essential tools used in mobility electronics. Yet, FA’s role is underestimated and underutilized. Its administration lacks standardization and support, esp., during multi-stress accelerated reliability testing (ART). Proposed three-stage systemic early FA (SEFA) methodology provides feedback using conventional and original systematic hierarchical complementary multidisciplinary comparative tools and methods focusing on prevalent early failures (EF). Subject matter result-oriented technical root-cause FA (RCFA) is a vital past of SEFA. This paper outlines three-phase RCFA methodology along with specific methods, tools, and examples related to ART. Presented EF classifications interpret EFs’ symptoms, mechanisms, and causes and propose corrective actions. Suitable RCFA-SEFA improve products and ART by precluding-resolving prevalent EF.