Three successive ESPs have been installed in a horizontal well in the Rijn oilfield, offshore The Netherlands. Very soon after installation of the first completion, the ESP started to gaslock. Operational procedures based on data analysis were setup in an attempt to suppress the gaslocks and to prolong the runtime of the first ESP, but without success. Nodal analysis revealed that the second ESP would benefit from a better tubing lift performance. Although the average runtime of the second ESP improved considerably, the ESP still exhibited unstable performance and kept suffering from periodic gaslocking. Transient numerical simulations were made in order to gain insight into the multiphase flow behavior underlying the well's instability and assisted in selecting appropriate hardware for the third completion. The ESP in this final design is currently operating very stably and reliably and does not show any gaslocking anymore; the combination of thorough data analysis, revised operational practices, and dynamic simulations, resulted in a trip-free ESP completion. This paper aims to be a concrete reference case for operators with ESP lifted horizontal wells, suffering from pump instability. As part of the practical recommendations for other operators, key findings from the dynamic modelling (recognizing the ESP-well instability mechanism) and operational response to ESP trips (successful quick-response workflow) will be elaborated on.