Half of all malfunctioning products returned to stores by consumers are in full working order, but customers can’t figure out how to operate the devices, a scientist said on Monday.

Product complaints and returns are often caused by poor design, but companies frequently dismiss them as “nuisance calls,” Elke den Ouden found in her thesis at the Technical University of Eindhoven in the south of the Netherlands.

According to the short article, the average American consumer will give it 20 minutes before giving up.