Less space after moving files I got the "startup disk full" message so I moved several of my massive folders to an external hard drive, deleted the folders I just moved off my Mac and yes, emptied the Trash bin.

It then said I had 83.14 GB of free space (I previously only had two!) And THEN, I moved another folder full of videos I had previously overlooked, it was 14 GB, deleted the folder from the Mac and emptied the Trash but then when I went to check the space it said 79 GB of free space! 4 GB LESS free space after moving and deleting a 14 GB folder!!!

How is this possible?
The last few times I had issues like you describe, I emptied trash and rebooted. I found that certain video apps left a cache that was gone after rebooting.