After the mid-point where the hero achieves a False Victory, things start going downhill from that point on. This is how to speed up your hero’s decline to make the climax that much more exciting in contrast.
The fifth 15 minute segment occurs right after the midpoint of the movie, which is where the hero achieves a False Victory. This is the time when the villain starts to gain the upper hand while the hero starts to fail. What the fifth 15 minute segment needs is an Inciting Incident that casts doubt in the hero’s quest, a steady decline in the hero’s fortunes, and a climactic ending where the hero still manages to achieve a minor victory that overcomes the current problems, but doesn’t help solve the main goal.
In “Bolt,” the Inciting Incident occurs when Mittens the cat teases Bolt that he doesn’t have superpowers, so Bolt barks his head off, which attracts an animal control officer, who puts Mittens and Bolt in a cage and takes them away to a shelter. The Rising Action occurs as Bolt struggles to face the fact that he doesn’t have superpowers. After escaping from the animal control truck, Bolt realizes that he needs to rescue MIttens. The Climax occurs when Bolt successfully breaks Mittens out of the animal shelter.
Although the hero does achieve a victory, this victory is more due to overcoming a problem rather than working towards achieving the main goal. In “Die Hard,” the Inciting Incident for this segment occurs when the FBI and SWAT team shows up. The Rising Action occurs when the SWAT teams moves into place when the terrorists blow up the police department’s armored car. The Climax occurs when Bruce Willis uses some of the terrorist’s dynamite to blow up some of the terrorists.
Like in “Bolt,” Bruce Willis achieves a minor victory at the end of this segment, but this victory brings him no closer to his goal than when he started. This victory is more like treading water than getting the hero closer to a final victory.
Breaking down this part of your movie, the fifth 15 minute segment ends with a minor, but meaningless victory. The hero keeps getting further away from his (or her) goal.