Parts not unloading with StreamingEnabled

I have a huge railroad game which is unplayable without a render distance limitation. My first inclination was to use StreamingEnabled, and that’s what I did, but the parts don’t unload after you cover them. I expected that once I moved far enough away, the parts behind me would unload automatically, but that wasn’t happening. This is my issue here:

The first image is what you see when it is not rendered. As you can see, I have 60 frames per second.

This is after I used my train to cover the whole map, and now I have 20 frames per second, and everything in the back is still loaded.

I need to unload old parts once they are out of my range since the lag racks up quickly if I don’t.

Can I force parts to unload with StreamingEnabled, or do I need to create a manual unloading system?

These are my Streaming settings.

image

I’m bumping this post because I need this project to have progress made. My entire developing team has paused due to this terrible lag.