Isolate one variable at a time. Apply the same label stock to a known-good surface such as clean glass and condition it; if it holds, the container surface is suspect, so check for mold release, slip additives, texture, or a resin change. Next, apply the same stock by hand with firm pressure and compare it with line-applied labels; a difference points to applicator pressure, dwell, or surface temperature. Finally, test an alternate adhesive class on the failing container. Record the results in the SKU spec so the finding survives staffing and supplier changes.