Scene Rebalance yields different result than what was previewed (Izotope RX 12)

I have a piece of music from a movie that I'm attempting to take the FX out of. The cue is mostly just music with a few steps/doors in the background. When I select just the FX sound I want to take out and preview the Scene Rebalancer tool using 0.0 for dialogue and music and -59.55 for FX - it sounds fantastic. Then when I click render, the result is a barely audible sound.

I have also noticed that the longer section I select, the more true to the preview the scene rebalancer tool is. Is this a known issue? Is there something I may have wrong in the settings or order of operation?