During the sinking of prefabricated shafts constructed by the mechanical method under complex hydrogeological conditions, end-resistance fluctuations are large, and circumferential eccentric loading is aggravated, these cause difficulty in identifying their underlying causes. To address these challenge, a case study is conducted on a prefabricated shaft project on the Guangzhou East Railway Station-Huadu Tiangui Station Intercity Railway, and a multi-source monitoring dataset is established, including eight-point circumferential contact pressure at the cutting edge, reinforcement stress in the lining segments, and groundwater level/pore-water pressure. Methods such as mean contact pressure, coefficient of variation, pressure-stress regression, and time-series comparison are employed to investigate the staged evolution of sinking resistance, circumferential load nonuniformity, and the influence of groundwater fluctuations. Results are obtained as follows: (1) The cutting-edge contact pressure generally increases with burial depth and exhibits clear stage-wise characteristics. (2) Under the influence of strongly weathered granite and isolated boulders, both the pressure peaks and dispersion increase markedly, and local long-tail distributions appear. With increasing depth, the circumferential load pattern gradually changes from nearly uniform distribution to local concentration, and the coefficient of variation rises abruptly at certain stages, indicating a pronounced increase in eccentric loading. The cutting-edge contact pressure shows a strong spatial correspondence with the reinforcement stress of Ring 0, and the two are positively correlated overall. A small number of high-stress anomalies primarily occur in zones where resistance surges and eccentric loading intensify. Pronounced groundwater-level fluctuations are broadly consistent in time with pressure anomalies, indicating that water-level changes can alter the distribution between sidewall friction and end resistance through delayed pore-pressure dissipation, effective-stress adjustment, and changes in the stability of the slurry jacket. Mean contact pressure, coefficient of variation, and pressure-stress anomalies can therefore be used as monitoring indicators for identifying sudden changes in end resistance, the development of eccentric loading, and local internal-force anomalies.