: Failed limit switch, broken actuator tongue, or failed 24V DC input module on the PLC board.
The manual explicitly calls for heavy maintenance every six months:
Remove the hard drive from the PC unit inside the operator panel.
And pinned at the top was a thread with 847 replies. Its title:
Check the high-speed bus cables (MELDASNET or optical fibers) for sharp bends or pinching. 5. Advanced Troubleshooting & Hidden Diagnostic Screens
The manual provides rare "how-to" instructions for critical back-end tasks, such as unlocking password-protected screens, erasing memory (SRAM clear), and updating system software.