To optimize the construction procedure, shaft alignment is performed during the initial phase, when most of the stern area and superstructure are not completed and most machinery, including the main engine, is not yet installed. The subsequent installation and welding of the hull structures may result in the deformation of the vessel’s structure relative to the original sighting condition, including the stern tube casting, and the foundation of the main engine and intermediate bearings. While the final vertical positions of the intermediate bearings and main engine bearings can be adjusted during jack-up tests to match the shaft alignment load calculations, the final slope angle of the aft stern tube bearing cannot be directly verified. Thus, the occurrence of aft stern tube bearing slopes deviating significantly from the design, when measured through sighting after years of service, has become frequent. This paper investigates two case studies, which present the findings from laser-sighting measurements on two series of sister vessels that required extensive repairs during drydock due to significant damage to the aft stern tube bearing after several years of operation. The results showed a similar pattern in stern tube casting deformation among all the vessels within the series, suggesting an issue originating at the new building stage. It is conjectured that unaccounted hull deflections after the initial sighting may result in a pattern where the stern tube casting may exhibit an unaccounted negative slope. This unaccounted casting slope might go undetected if a clearance measurement at the aft edge of the aft stern tube bearing is not performed before the propeller fitting, or if a final sighting is not conducted after the main engine positioning and the erection of the aft structure. Consequently, this could lead to accelerated wear and possible failure of the aft stern tube bearing if the bearing slope design is not compensated accordingly.