I have several large events that I'm copying to external hard drives, but for some reason the act of copying isn't keeping my computer from going to sleep, so I have to wake it up in order for it to resume the copy properly.
Is there a setting somewhere where I can assure that if the computer is busy doing something it won't pause in the middle like that?
The only certain way to get this resolved is to disable system sleep. There are a couple of cheater tools out there that mimic keyboard or mouse activity, but they haven't always worked in my tests. My systems are all set to sleep the monitor after 30 minutes, but they are all set with the system to not sleep - ever.
Also, if you haven't already, be sure to disable "App Nap" for FCP X (single click / select App icon, select "Get Info", check the box in the info panel).