For more blatant issues I would have tried that. For a faint white streak through a scan? Never occurred to me. And the help bot specifically said to unplug the power cord, not turn off the machine. So even when "off" there must be some low-level function that's maintained by the power input. Specifically, it said to unplug it and leave it unplugged for at least one minute.
Other stuff? It'll make you nuts. I have (make that "had') a nice-looking Baskerville font that I was gearing up to use on a project. Everything looked great on the screen. I printed a test sheet, and it came out looking like what we used to get in the old days when you printed to an Epson printer but the system was set up to use IBM printer codes -- gibberish. I tried a couple of different Baskerville fonts from other sources, and they print fine. So I uninstalled the problem font. Of course, the font metrics on the other versions are different, so now everything has to be re-formatted.