Not the CPU emulator, the GPU emulator. The game is asking the GPU to render an object, which requires it to provide three coordinates. However, the game never

Not the CPU emulator, the GPU emulator. The game is asking the GPU to render an object, which requires it to provide three coordinates. However, the game never initialises the first of these coordinates, so the emulator was drawing an object with the first coordinates initialised to garbage values, because for every new object draw call the emulator was discarding the previous state. On the real hardware it seems that the hardware simply reuses the coordinates from the previous object, so the fix in the emulator was simply to move the coordinates from being local to the function (in which case they're reinitialised on every call) to being global (in which case they remain populated with the previous values between calls).