Most software bugs are dramatic. A database locks up, a payment webhook drops on the floor, or an OAuth token expires in the middle of a demo.

Barcode bugs are not dramatic. They are passive-aggressive.

Everything looks gorgeous on your 5K monitor. Then you hit Print, peel a sticker off row 9 of an Avery 5160 sheet, and the bottom guard bars are sliced clean across the perforation line. Or worse: you run a thermal roll through a 203 DPI Zebra printer, the label looks crisp to your human eyes, and the fulfillment center scanner refuses to beep.

Over the past couple of weeks building and rebuilding UPCLabelMaker , we spent an embarrassing amount of time chasing tiny, stubborn physical-world bugs like these. Not AI prompts. Not distributed consensus. Literally tenths of a millimeter of black ink on sticky paper.

Here are four of the dumbest, most interesting traps we hit—and how we fixed them after actually decoding and measuring every single generated file.

1.…