In a cohort study conducted, researchers wanted to determine if the global alignment and proportion (GAP) score, SRS-Schwab, and Roussouly theoretical apex of lordosis could accurately predict mechanical difficulties in adults with spinal deformity (ASD). Achieving adequate sagittal alignment in ASD surgery was crucial to achieving positive results. Mechanical difficulties were thought to be caused mainly by postoperative spinal alignment. Over a 5-year period, a retrospective review of consecutive primary ASD cases underwent deformity correction in the same institution. Logistic regressions were used to examine the relationship between the 6-week postoperative spinal alignment classification and the occurrence of mechanical problems at the last follow-up. In addition, the receiver operating characteristic (ROC) curve analysis was used to evaluate the discriminant capacity. Mechanical issues were reported in 58.3% (N=49/84) of patients, and 32.1% (N=27/84) required revision surgery. The GAP score had little discriminant ability to predict problems (AUC=0.53, 95% CI=0.40–0.66, P=0.58). In contrast, the SRS-Schwab sagittal modifier score (AUC=0.67, 95% CI=0.54–0.79, P=0.008) showed a statistically significant (although moderate) predictive value for mechanical problems. At 6 weeks postoperatively, there was a significant link between pelvic tilt (PT) (P=0.03) and sagittal vertical axis (SVA) (P=0.01) and the occurrence of subsequent mechanical problems. The matching Roussouly theoretical apex of lordosis had no significant relationship with the ultimate outcome (P=0.47). The findings highlight the complexities of mechanical failure and the high possibility that causal factors are multifaceted and not limited to alignment. Therefore, the GAP score should be utilized with caution because it may not explain or predict mechanical failure in all populations as expected based on alignment. In order to develop a universal score that can be used for all populations, future studies should focus on etiology, surgical methods, and patient characteristics.