I'm having the strangest issue and I'm so puzzled by it.

I have a couple of song files with some random chords in it for practice. These suddenly won't play realtracks. They worked fine before.

The tracks are enabled.
The meters indicate playback, but the master volume fader does not.
Realtracks work on other biab song files.
I'm pretty sure it's not a setting related to the audio (interface), seeing as it plays fine on other files.
I have rebuilt the realtracks library several times, no solution.

Does anyone have an idea of what the cause could be? The song files absolutely worked fine before. The video
below explains my issue in more detail. Any assistance would be greatly appreciated.