I have reports that are scheduled to run from classic. Recently (about 6 months ago), they started trying to run from the sandbox as well, which results in an error email to me. I turned it off by going to the sand box and saying not to email (sorry I don't remember exactly how I did this), but when I updated the sandbox the change reverted (of course). It's not that big of a deal to get the error emails, but I would rather not.