I have moved all of my games and apps to either an external SSD drive or an Xbox Memory Card. I initially did have some remaining "hidden" DLC content left on the Internal drive that I removed with the Free Up Space option. It did free up more space, however I am still somehow "missing" about 100GBs of memory and it would appear that there is nothing left on the drive?
I know the Xbox reserves about 200GBs of the 1TB drive space standard for the OS, System Updates & Quick Resume, but I am unaware of it using any further drive space?
Things I Have Tried
I have Cleared the System Cache
I have Cleared Local Saved Games
I have Cleared local Xbox 360 storage
I have Cleared Persistent Storage in Blu-ray
As you can see I only have one 30 second video (1080p) and one screenshot (4k HDR) on my local storage.(So maybe 200MBs being extra generous?)
I really don't know what could be taking up that space, and I have no idea how to get it back, short of possibly doing a complete console reset? Which, I am really trying to avoid because I'll have to set up all of my console preferences and settings again... but I will if it's the only way.
I found some older posts with a similar issue but no one seemed to have a solution besides the things I listed above that I have already tried and did not work. I hope this post can find a solution or at the very least make it more clear for someone else in the future who may have this issue.