Energy plays a key role in human daily activities, thus crucially serving in people's development, be it social or economic. In line with the current world-wide renewable energy resources promotion, Pumped Storage Hydropower-based Electricity generation has been a widely adopted practice, where Reversible Pump Turbines (RPT) present many advantages over other formally used electromechanical devices. However, investigations have shown that reversible pump turbines operations are associated with different flow instabilities, where induced pressure fluctuations can cause structural vibrations and possible machine performance degradation. This article reviews the already accomplished studies and their findings on RPT flow stability, its development mechanism, and influencing parameters, where some light were shed on remaining gaps for further investigations.