It seemed to me in past games the LD and RD are programmed to "auto-reset" back to their original positions after they get caught up-ice, etc. That seems to be what's happening in the second vid.
Keith is on the right side, and should stay there and cover the two Red Wing players in the right faceoff circle. But he inexplicably vacates his defensive position to skate across to the left side of the ice. Meanwhile, Seabrook, who is on the left side and inches away from the puck carrier, completely ignores him and cuts back to the right faceoff circle.
Like I said, the problem here appears to be that CPU players are programmed to auto-reposition themselves, regardless of what's happening in the midst of the play. If that's an A.I. programming issue on the lower difficulty levels, it's no doubt going to happen on the higher levels.