I kept searching and finally found an article which explains what was going on: What is the Barcode Conspiracy Theory? Explanation, Meaning, Definition - Bedeutung Online

Barcode conspiracy theorists believe that the barcode on food emits dangerous radiation when scanned at the checkout, and that people need to protect themselves from it. According to them, the radiation emitted not only degrades the quality of the food, but is also harmful to humans. According to the barcode theory, harmful vibrations are released during the scanning process, which are transmitted to the human body. With interference suppression, the harmful effect can supposedly be neutralised. The interference suppression is done in the simplest way: According to this, it is sufficient if the barcode is crossed out.

All right.