  The Binder cumulant (BC) has been widely used for locating the phase
transition point accurately in systems with thermal noise. In systems with
quenched disorder, the BC may show subtle finite-size effects due to large
sample-to-sample fluctuations. We study the globally coupled Kuramoto model of
interacting limit-cycle oscillators with random natural frequencies and find an
anomalous dip in the BC near the transition. We show that the dip is related to
non-self-averageness of the order parameter at the transition. Alternative
definitions of the BC, which do not show any anomalous behavior regardless of
the existence of non-self-averageness, are proposed.
