You have a software or hardware problem. If you have a video card I would remove it, uninstall the drive and see if you are still getting corrupt frames.
If that doesn’t work I would do one of two things.
A)
Uninstall FCP, reinstall, if still a problem, wipe HD and to a total reinstall from the ground up.
or
B) take the system to Apple and have them look at the graphic card.