This is what I posted in a different topic addressing the same issue:
Another way to get them back in the "scheduled" list is to force a reboot of the Media Server STB. "Main Menu -> Customer Support -> Top Support Tools -> Reboot STB". After reboot, the box apparently rescans the guide and will re-discover the missing scheduled recordings.
Not an idea solution, having a fix would be that, but at least you don't have to fiddle with each and every series affected, just force reboot the box. This has worked for me several times. If fact, I've gotten into the habit of rebooting the box before going to bed.