Abstract: The search for chiral magnetic effects (CME) in relativistic heavy-ion collisions helps us to understand CP symmetry breaking in strong interactions and the topological nature of the quantum chromodynamic (QCD) vacuum. A two-plane method was proposed based on the fact that the background and signal of CME have different correlations relative to the spectator plane and the participant plane. Using a multiphase transport model with different input strengths of CME, we revisit the two-plane method in isobar collisions at \sqrts__\rm NN = 200 \;\mathrmGeV. The relative correlations of the CME signal and background to two different planes were found to be different, which is inconsistent with the assumptions made in the current experimental measurements. The difference arises from the decorrelation of the CME relative to the spectator and participant planes, which originates from the final state interactions. Our finding suggests that the current experimental measurements may overestimate the fraction of the CME signal in the final state in relativistic heavy-ion collisions.