What MissTickly fails to understand, because she clearly knows very little about printers, is that the “wet” toner (which is specifically heated, excess toner for those who freaking care) could have transferred to the back of the long-form right after it printed. The documents didn’t have to be folded together in order for the transfer to take place.
What causes extra toner? Does it happen often? What makes it transfer, and is there a point at which it’s no longer transferrable?