Interior areas of Nether Fortresses do not generate

Rooms and Corridors of Nether Fortresses do not generate

What I expected to happen was...
Nether Fortresses always generate with an exterior section which includes bridges, walkways and blaze spawners. They also generate with an interior section which includes corridors, loot chests and nether wart. The lava well room connects the two sections.

What actually happened was...
Upon loading a Nether Fortress, it did not generate the interior section at all: corridors, chests or nether wart. There were only bridges, walkways and blaze spawners. The lava well room led to nothing.

Steps to Reproduce:
1. Load the Nether
2. Load a Nether Fortress
3. There might be no interior section.