Q: Emptied trash but still reporting it's over 3 GB in size with 0 items

Please try again to post the screenshot.

If any external drives are connected, please unmount and disconnect them. Any change?

Try a restart.

This procedure is a diagnostic test. It makes no changes to your data.

Please triple-click anywhere in the line below on this page to select it:

ls -@Oaen {,/V*/}.Tr* | pbcopy

Copy the selected text to the Clipboard by pressing the key combination command-C.

Launch the built-in Terminal application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.

Paste into the Terminal window by pressing the key combination command-V. I've tested these instructions only with the Safari web browser. If you use another browser, you may have to press the return key after pasting.

Wait for a new line ending in a dollar sign ($) to appear below what you entered.

The output of the command will be automatically copied to the Clipboard. If the command produced no output, the Clipboard will be empty. Paste into a reply to this message.

The Terminal window doesn't show the output. Please don't copy anything from there.

If any personal information appears in the output, anonymize before posting, but don’t remove the context.

Restart the computer in safe mode. Certain caches maintained by the system will be rebuilt.

Safe mode is much slower to start up than normal.

When the login screen appears, restart as usual (not in safe mode) and test. There's no need to log in while in safe mode.

Note: If FileVault is enabled, or if a firmware password is set, or if the startup volume is a Fusion Drive or a software RAID, you can’t start in safe mode. In that case, ask for instructions.

Back up all data.

Triple-click anywhere in the line below on this page to select it:

~/Library/Caches/com.apple.finder

Right-click or control-click the line and select

Services ▹ Reveal in Finder (or just Reveal)

from the contextual menu.* A folder may open with an item selected. If it does, move the selected item to the Trash, then  relaunch the Finder and empty the Trash. Test. If there's no improvement, repeat with this line:

~/Library/Preferences/com.apple.finder.plist

Move the selected item to the Desktop, leaving the window open. Log out, log back in, and test. If there's no change, put the item you moved back where it was, overwriting the one that may have been created in its place, and log out again. Otherwise, delete the item you moved.

*If you don't see the contextual menu item, copy the selected text to the Clipboard by pressing the key combination  command-C. In the Finder, select

Go ▹ Go to Folder...

from the menu bar and paste into the box that opens by pressing command-V. You won't see what you pasted because a line break is included. Press return.