A printer firmware update kept failing. Vendor support's diagnosis pointed at a faulty SD card.
The DataFlex 6330 has no SD card. It uses onboard memory only. The vendor's diagnosis was likely templated from a different DataFlex variant or a generic Videojet response. Following it would have produced no progress. Trusting it would have produced months of stalled tickets. The fix was to physically open the hardware and verify what was actually inside it.
How it surfaced. Disassembled, inspected, and cleaned a spare unit instead of trusting the diagnosis.
How it got fixed. Spare upgraded cleanly. Production unit upgraded the same way. Both units now match the rest of the fleet, without ever ordering the part the vendor said was the problem.