The reliability of a Production Control System impacts productivity; research suggests that Last Planner System - reliability could be improved with a variability analysis and control of its subprocesses. The variability ratio of those subprocesses, known as the Bullwhip Effect of Conversations, helps to quantify the conversation flow between the Last Planner System subprocesses. We assessed if the first stages of the Bullwhip Effect of Conversations evaluation methodology could be used as a weekly tool, to measure the proper application of Production Control System-subprocesses. This paper reports the analysis of conversations trends, statistical controls and the impact of the Production Control System subprocesses using two case studies: one carried out in South America which used the Last Planner System, and one in Europe which used the Traditional Production Control System. We found production control subprocesses which were under statistical control, and that impact one another as well as the PPC. With this methodology, it is possible to evaluate the stability of the coordination flows into each Production Control System-subprocesses. Both cases were stable, predictable and free of external causes of variation. We consider that this method could be valuable for tracking and tuning the application of Last Planner System subprocesses.