In order to design Petri net (PN)-based liveness-enforcing supervisors to deal with flexible routes and assembly operations in automated manufacturing systems (AMS), a deadlock prevention policy was proposed in Hu et al. (IEEE Trans Ind Inf 9:109-121, 2013). The proposed policy exploits the structural analysis of PN models of AMS in the sense that the liveness of a PN model is attributed to the absence of undermarked siphons. To demonstrate the applicability and effectiveness of this method, a few examples were utilized. Some liveness-enforcing supervisors computed in Hu et al. (IEEE Trans Ind Inf 9:109-121, 2013) to enforce liveness on the considered Petri net models do not provide live system behaviors. The purpose of this paper is to report these facts and to provide the correct results.