Then she saw it. In the HMI’s Alarm view configuration, she’d set up a sneaky little debug feature weeks ago—a hidden diagnostic screen that logged internal HMI script errors. She navigated there now.

First, online, she forced the PLC back to RUN. A single click. The diagnostics buffer logged it instantly:

Line 47. She opened the HMI script editor. There it was: a line of VB that wrote a timestamp to a custom property on a graphic IO field. A field that was conditionally visible. If the filler was in manual mode, the field didn’t exist. And if the field didn’t exist…