External HDs are showing twice in finder

Hi wojciech219,

Thanks for contacting Apple Support Communities!

We understand that your drives are displayed twice in the Finder. To help us isolate the issue, which can lead to a resolution, we have some questions:

• Are you able to open both copies?

• What happens when you eject one? Does one still remain? Or do both drop off?

• Are the drives partitioned?

Are you able to drag one of the drives from the Finder window? This article will show you how: Customize the Finder toolbars on Mac

"Customize the sidebar

1. On your Mac, click the Finder icon  in the Dock to open a Finder window.
2. Do any of the following:

• Hide or show the sidebar: Choose View > Hide Sidebar, or View > Show Sidebar, in the menu bar. (If Show Sidebar is dimmed, choose View > Show Toolbar.)
• Resize the sidebar: Drag the right side of the divider bar to the right or left.
• Change what’s in the sidebar: Choose Finder > Settings, click Sidebar, then select or deselect items.
• Rearrange items in the sidebar: Drag an item to a new location.
• Show or hide all the items in a section of the sidebar: Position the pointer over the section heading until the Hide button  or the Show button  appears, then click the button. For example, to temporarily hide your Favorites, position the pointer over the Favorites heading in the sidebar, then click the Hide button .
• Add a folder or disk to the sidebar: Drag the item to the Favorites section. If you don’t see the Favorites section, choose Finder > Settings, click Sidebar, then select at least one item in the Favorites section.
  • Adding an item to the Finder sidebar only creates a shortcut to the item; the item isn’t moved from its original location.
• Add a file to the sidebar: Press and hold the Command key, then drag the file to the Favorites section. If you don’t see the Favorites section, choose Finder > Settings > Sidebar, then select at least one item in the Favorites section.
  • Adding a file to the Finder sidebar only creates a shortcut to the file; the file isn’t moved from its original location.
  • Add an app to the sidebar: Press and hold the Command key, then drag the app icon to the Favorites section.
• Remove an item: Drag the item’s icon out of the sidebar until you see the remove sign .
  • The link to the item in the sidebar disappears, but the item remains in its original location on your Mac."

We look forward to your reply.

Cheers!

Hello wojciech219,

We'll need to isolate the issue a bit more. To do so, we'd like to have you test to see if the same issue occurs within a different user on your Mac. If needed, you can use the steps in Add a user or group on Mac to create a test user.

1. On your Mac, choose Apple menu  > System Settings, then click Users & Groups  in the sidebar. (You may need to scroll down.)
2. Click the Add Account button below the list of users on the right (you may be asked to enter your password.)
3. Click the New Account pop-up menu, then choose a type of user. (Administrator) 
4. Enter a full name for the new user. An account name is generated automatically. To use a different account name, enter it now—you can’t change it later.
5. Enter a password for the user, then enter it again to verify. Enter a password hint to help the user remember their password.
6. Click Create User.

Once you've created a test user, let us know if you continue to see duplicates within Finder. We'll go from there.

Regards.