iMac says Storage is full but I only used 10GB out of 1TB of storage...? This is very weird. New iMac. 4 months old, brand new. 1 Terabyte of storage. The Mac keeps saying I am out of storage, but when you add up all of my word docs, downloads, applications, etc., it only totals about 10Gb. Then when I click on "manage storage" it gives me a breakdown of what my computer is using and at the bottom line it says "system: 990 GB" - Shouldn't the system be operating at about 8-9GB tops?!!? I have deleted all surplus items and literally the total of all downloads, documents, files, applications, etc. is only about 10GB but it says my storage is almost full!! Please help!

I put up a photo of the storage management screen before I deleted some more stuff.... This is nuts.
This happened to me once. I used Daisy Disk to figure out where the disk usage was coming from.

In my case, there was a problem with the coresymbolicationd cache, which was growing indefinitely (eating up hundreds of gigabytes).

After deleting /System/Library/Caches/com.apple.coresymbolicationd, everything returned to normal.