We investigate the response of magnetic tunnel junction (MTJ) devices based on GlobalFoundries 22FDX¹ embedded-magnetic random access memory (MRAM) technology to external thermal and magnetic stress. An anomalous reversal of the reference system was observed in some devices when subjected to a constant static external magnetic field at temperatures as high as 150 ∘C. The strength of the external magnetic field, ambient temperature, MTJ diameter, and composition of the synthetic antiferromagnet (SAF) reference system all affect the severity of the reference system’s instability. In this study, we show that while a SAF reversal in single-bit MTJ devices reverses the direction of their R–H hysteresis loop and so their switching field and offset field polarity, it does not significantly impact their electrical switching behavior. Furthermore, we experimentally show that the functionality of 40-Mbit MRAM arrays with a pitch of approximately 200 nm remains unaffected by the SAF configuration and consequent offset field polarity of the individual devices.