Today immediately before I closed my laptop, I had printed 2 copies of a PDF file. Then about 2 hours later, I opened my laptop again and the printer started to generate a large pile of mostly blank pages for no apparent reason. However, some of the pages had garbled UTF-8 characters all over them.
For what reason, if any, would my printer be doing this? I can provide specs on the printer, my laptop, or my home network configuration on request if necessary, though none of those have been customized in any special way that I think would be relevant to this.
This is quite easy - I bet this is a network attached printer: You closed your laptop while the print job (or some trailing data) was still being sent to the printer - this stopped the transmission.
When you reopened your laptop, it duly went on sending the remaining data, but the printer had in the meantime discarded the half-sent data because of a timeout or disconnection event, so the remainder (binary data) was completely out of context, prompting the printer to try and parse it, which it did with dire consequences.