Finder Freezes up & can't access External Drives

If a simple reboot of your Mac doesn’t fix things, see if the problem still happens in Safe mode (press and hold the shift key down at startup). It can take much longer to safe boot (5 min) so be patient.

How to use safe mode on your Mac - Apple Support 

Safe mode is non-destructive to user data. It’s not a cure-all, but very often corrects weird software behavior by forcing the OS to do cache clearing and other housekeeping. When you're in safe boot, the machine will not be at its best performance, especially with graphics, but that's expected.

Does the problem persist while in Safe mode?

Exit safe mode by restarting your Mac normally and re-evaluate the issue again.

Also, this may be an issue with your hard drive. Try booting in Recovery mode and running the Disk Utility First Aid routine on the startup drive.

• Shut down the Mac. Then press the power button to reboot and immediately press and hold the Command and R keys (⌘R) until you see the Apple logo and progress bar.

• When the macOS Utilities window appears, select Disk Utility, click View > Show All Devices. Select the top-most device and click First Aid. Also run First Aid on any indented drive volume listed below that device.

With luck this will repair any issues that it discovers and get you back on track.

For additional guidance, please see: How to repair a Mac disk with Disk Utility - Apple Support

As den.thed suggests below, launch Disk Utility, reconnect the drive and run First Aid on the device and any volumes on it. With luck any issues found will be corrected.

How old is this drive?

If it's more than 5-6 years old, there's a good chance the drive has developed some internal problem of failure. Seasoned users will recommend that you run drive diagnostic. DriveDX from Binary Fruit is one that is often recommended. If it finds any problem with the drive, then you'd be advised to backup that drive asap and replace it.

If Disk Utility or DriveDX find no issue, the problem may be the connecting port or cable or enclosure.

Try connecting the drive to different ports on the computer.

If the cable can be separated from the drive enclosure, then try another cable. If the cable is permanently affixed, then you may need to acquire another external enclosure for the drive inside.

Is the drive connected to the Mac through a hub or dock?

If so, try connecting it to the Mac directly.

Is this a bus powered drive? (Does is get its power from the Mac?)

If so, a better option would be to purchase an enclosure that comes with an ac adapter for power rather than relying on the computer. See BDAqua's post above.

How does the Mac behave when you boot and run it with ALL of the external drives and peripherals (hubs/docks, printers, etc) disconnected?

I know that's not how you normally run because your user files are on the external drive, but it is important to know if that affects the issue. Give that a try and let us know the results.

Are these drives Bus powered, no A/C power of their own?

Apple Icon>About this Mac>System Report>Hardware>USB, how many mA are being used...

Yea' I've had funky external drives freeze up both Finder and Disk Utility.

Most of the time a yank of the cord, a reconnect and Disk Utility First Aid would fix the problem. If not and if after a couple of attempts to erase and reformat, the external drive went into my box useless junk.

I see in your reply above to BDAqua re: Current required mA... that's the same that I see on my MBP w an OWC Express enclosure, and I have no issue at all w mine. That is right at the edge of Current available, so not sure what that means. Probably can't have two on the bus (?).

If Disk Utility cannot run First Aid because a volume cannot be unmounted, that's an indication of data corruption. This appears to be an APFS formatted drive. Can you delete the troublesome APFS volume? You might give that a try before wiping the entire device.

Add, delete, or erase APFS volumes in Disk Utility on Mac - Apple Support

If at all possible – I know your Mac is freezing – backup that drive. Then erase and reformat it and start over with whatever you are using it for.

Did you consider running the DriveDX diagnostic app?

Have you installed and run any "cleaning", "optimizing", "speed-up", anti-virus or VPN apps on your Mac?

Similar to what D.I Johnson say's... I was thinking that you should test one drive at a time to see if you can narrow the problem down to a specific drive.

ESPEER wrote:

...

if i reformat this drive (after hopefully getting my work off it first) can I even trust this won’t happen again?

No, you cannot trust it won't happen again. All drives fail and corruption happens... we just never know when it will happen.

This is why it's so very important to have backups of your data. The more backups the better. Apple has built the Time Machine backup app into the macOS. Another very popular option is Carbon Copy Cloner from bombich.

How important is your data to you?

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