I watched the video couple of days ago. I remember that it sounds like a computer glitch. The plane suddenly pitched up and down so violently (that's when the high G happened) that the two lost the control stick, and almost blacked out, one even bump his head in the glass. The whole thing lasted 26 seconds. In the end, one pilot got hold of the stick and pulled the plane back to normal.
Wow, that would cause you to be a little jumpy, doesn't happen very often, but OH Boy, that would wake you up! Player, I guess thats what the old heads meant when they said flying was hours and hours of boring, with a few minutes of sheer terror thrown in! Wow, good airmanship and at least they and their aircraft are safe.