Antiferromagnetically coupled (Co/Pt)/Ru multilayers with perpendicular anisotropy have been shown to exhibit both vertically and laterally correlated magnetization reversal modes. In this work, the magnetization reversal of a multilayer film whose layer thicknesses have been tuned to be at the phase boundary between the two reversal modes has been investigated as a function of temperature, using the first-order reversal curve (FORC) method. At high temperatures, reversal via vertically correlated stripe domains throughout the film thickness is observed, similar to that in Co/Pt films without the Ru spacers. At low temperatures, antiferromagnetic (AF) interlayer exchange coupling dominates, and laterally correlated reversal is observed with an AF coupled remanent state. Under magnetic field cycling, dipolar fields can transform the sample back into a vertically correlated domain state, thus leading to an exotic behavior with FORC's existing outside the major hysteresis loop. Calculations show that the laterally correlated reversal mode is indeed slightly more stable, and the crossover to vertically correlated reversal can be induced by temperature as well as magnetic field.