"Game 5 is just Game 4 with a little extra wrinkle. Now a second back-door path X←B←C→Y needs to be closed. If we close this path by controlling for B, then we open up the M-shaped path X←A→B←C→Y. To close that path, we must control for A or C as well. However, notice that we could just control for C alone; that would close the path X←B←C→Y and not affect the other path." (Pearl, p. 162)
Here we have the causal Bayesian network corresponding to Game 5:
Select Main Menu > Analysis > Visual > Graph > Influence Paths to Target
and see that there is a noncausal path that needs to be blocked.
You can block this path by fixing the probability distribution of variable C.
You can check if this proposed approach is correct by setting your evidence — Fix Probabilities on C — and then running the Influence Paths Analysis again.