Background <p>Triply periodic minimal surface (TPMS) lattices offer exceptional multifunctional properties but often underperform mechanically compared to analytical predictions. The origin of this discrepancy remains insufficiently understood.</p> Objective <p>This study aims to identify whether the observed underperformance of TPMS structures stems primarily from geometric inaccuracies during fabrication or from intrinsic structural instability.</p> Methods <p>Schwarz Primitive TPMS lattices were additively manufactured using Carbon3D’s Digital Light Synthesis (DLS) process and characterized using X-ray computed tomography (XCT) for geometric fidelity. Compression experiments and nonlinear finite element simulations were then performed to correlate geometric deviations with mechanical performance. Parametric simulations were used to assess sensitivity to off-axis loading, and an external bracing concept was introduced computationally to enhance stability.</p> Results <p>XCT analysis confirmed that the printed lattices exhibited near-perfect geometric fidelity, with a voxel-wise Dice similarity coefficient of approximately 0.98 between the CAD model and the reconstructed geometry, yet compression tests revealed pronounced global buckling and high sensitivity to angular misalignment. Simulations demonstrated that as little as 1° of off-axis loading caused a &gt; 15% reduction in load capacity, while a simple cross-bracing strategy reduced this loss to &lt; 3%.</p> Conclusions <p>The findings show that mechanical underperformance in Primitive TPMS lattices originates primarily from buckling instability rather than print inaccuracy. The proposed XCT-based fidelity assessment and external bracing framework provide a robust pathway to improve the reliability of architected lattice structures across materials and manufacturing methods.</p>