While perovskite light-emitting diodes (PeLEDs) have demonstrated external quantum efficiencies (EQEs) well over 20%, their stability limits their commercial viability. Previously, the incorporation of transition metal dopants has demonstrated improved PeLED brightness, stability, and efficiency. Here, we dope Mn2+ ions into a quasi-bulk 3D perovskite and introduce tris(4-fluorophenyl)phosphine oxide (TFPPO) to achieve a 14.0% peak EQE and 128,000 cd/m2 peak luminance. However, while the incorporation of TFPPO dramatically increases PeLED EQE, their stability is severely compromised. At a 5 mA/cm2 electrical current bias, PeLEDs fabricated without TFPPO (2.97% EQE) and with TFPPO (14.0% EQE) decay to half their maximum luminance in 37.0 and 2.54 minutes, respectively. In order to investigate this trade-off in EQE and stability, we study both photophysical and optoelectronic characteristics before and after PeLED electrical operation. While Mn2+ doped PeLEDs hold the potential to enable bright and efficient lighting, device stability degradation mechanisms must be further investigated.