Pixel modules for the ATLAS ITk Pixel detector upgrade are currently undergoing production and quality control. During pre-production electrical testing, a recurring front-end chip communication issue was observed that could be bypassed by selectively disabling pixel core columns within the affected chips. The issue, designated as the "core column issue," has been documented across a large number of both ITkPix v1.1 and v2 modules. Since disabling a core column significantly reduces the number of operation pixels in a module, the prevalence of this failure could substantially impact ITk tracking performance.

The erratic behavior of the core column has led to difficulties in diagnosing its underlying cause. However, recent progress in visual inspection, combined with statistical analysis of production database records, points towards possible causes of the issue. This contribution highlights the discovery of, attempts to mitigate, production testing strategies, and current hypotheses of the core column issue.