Mac's hard drive is filling itself
I found what was actually filling up my disk.
/System/Library/Caches/com.apple.coresymbolicationd/
was 90G and growing.
I used DaisyDisk and analysed the disk in Administrator Mode (OmniDiskSweeper wasn't showing admin files).
I found on the internet that a lot of people had the same troubles.
Just open up a terminal and execute.
sudo rm -rf /System/Library/Caches/com.apple.coresymbolicationd/
For me it was a lot of old xcode app archives and device support for previous iOS versions.
I used DevCleaner for Xcode to free up a ton of space.
The app is free and was simple to use. I'm not affiliated in any way.