Thanks to Everything, I have discovered the culprit is Apple's CloudKit.

At random intervals of between five and thirty minutes, it is generating files of roughly 1.5GB in size in...

Thank you for the welcome, and for the suggestion. I will give Everything a run and report back any findings.

Just to update my issue, too: The opposite to what I reported occurred today. C:...

Hello,

My C: drive is progressively losing space the longer my computer is on. I am currently experiencing the worst example of it so far, which has prompted me to post this support request.


...