Floating eye win / loss condition [spoilers]
No, a hero breaking free of mind control does not itself make the game unwinnable for the traitor.
The Traitor's win condition for this haunt is exactly as follows:

You Win When ...
... all of the heroes are either dead or on the spaceship.

Note that if either of these happens to a hero, they are out of the game. Effectively, this means that the traitor wins when all heroes are unable to act. The &quot;can only mind control a hero once&quot; limitation simply means that any hero that breaks free of mind control must be killed for the traitor to win.