300GB is massive, and not every project is going to call every executable .dll (or any other) file.
An example:
To use MetaHumans you MUST have Visual Studio installed.
I had been using Unreal with zero issue, but the moment I started using the MetaHumans, I got stacks of errors.
This may be an issue you can side-step. Just keep in mind that if it IS core file corruption, even if you solve this issue, you could have more issues down the road… Or not.