DFT has become the dominant tool for electronic structure calculations due to its combination of favorable scaling and quantitative or semi-quantitative accuracy for a wide range of chemical problems. Nevertheless, it is not without systemic problems. Among these, perhaps the most pernicious and pervasive is self-interaction error (SIE), also known as delocalization error. Although SIE is most often associated with exaggerated delocalization of unpaired spins, including fractional atomic charges at stretched bond lengths, SIE produces a driving force to delocalize charge in closed-shell cases as well. It is especially problematic for solvated and condensed-phase ions. In the present work, we demonstrate how delocalization error interacts with the MBE to create a feedback loop leading to runaway error accumulation. The problem is most pronounced for semilocal functionals derived within the generalized gradient approximation (GGA), but is still serious for hybrid functionals such as B3LYP or PBE0, and meta-GGAs such as ωB97X-V 81 and SCAN. It signifi- cantly impairs the applicability of the DFT-based MBE.