A challenging operational problem of a condensate stabilization unit at Shell Bintulu is discussed in this paper. This unit operation consisting of multi-stage separation processes is employed in most gas processing industries to stabilize the separated liquids from the gas stream originated from well. Molecules of light components are removed through a multi-stage separation process with high, intermediate and low pressures (or stabilizer unit). The operational problem encountered in their operation of the stabilization was the reduction of its product capacity by half regardless increasing the inputs. In this study, we focus our investigation on the effect of pre-heater and fired furnace on the efficiency of stabilizer unit as suspected by experienced Shell staff. For this purpose, we develop a systematic technique and process analysis based on the principles of distillation and heat transfer to identify the root causes of the operational problem. The steady state operational data gathered from the current and past operations are used for the analysis. The analysis reveals that many correlated factors contribute to the product capacity problem, including the efficiency of pre-heater units, furnace and column internal operations, i.e. flooding and weeping. Based on the analysis results, we propose alternatives for improvement by considering some practical constraints in their industrial operations.