MacBook Pro: USB drive disconnects after update

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Level 1

8 points

MacBook Pro: USB drive disconnects after update

I have a Macbook Pro, 36Gb, recently updated to Tahoe 26.5.1. I've had an external 2Tb USB 3 drive connected for some time now, with 1TB set aside for Time Machine and the other 1Tb for manual backups.

It's been working fine, but since the update to 26.5.1 it disconnects intermittently - I get the "Disk not ejected properly" message and both partitions drop off the desktop. Sometimes they come back on their own a few minutes later, sometimes I have to unplug and reconnect the drive manually. More often than not, this happens while the machine is asleep, but it can also happen while I'm using it.

I've tried changing the USB port the drive is plugged in to, and I've tried a few different cables (USB-A and USB-C), but the problem persists. I've not changed the drive itself yet, because they're kinda expensive and until I can narrow down the problem some more I don't want to waste money if it may not be the drive hardware.

Anyone here know why this might be happening?

MacBook Pro (M3, 2023)

Posted on Jun 26, 2026 10:42 AM

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Answer 1

Jun 26, 2026 6:49 PM in response to pumbers

pumbers wrote:

It's been working fine, but since the update to 26.5.1 it disconnects intermittently

Were you running an earlier version of Tahoe and just installed a minor update patch?

Or were you running an older major version of macOS such as Sequoia?

Try changing the Privacy & Security System Settings for "Allow accessories to connect" and select "Always when unlocked", or perhaps temporarily change it to "Always"....the latter is more of a security risk when outside the home, but the former I don't think really impacts security in any meaningful way.

macOS Tahoe tends to require higher end cables than older versions of macOS especially for displays & external drives. The cables provided by the device manufacturers tend to be lower end cables.

Try connecting the external drive to the laptop using a powered USB3 hub to see if that makes any difference. I've seen multiple people on the Apple Discussion forums report having external drives work once they start using a USB3 hub. Years ago I had a Mac where connecting external drives would kill the Mac's USB port requiring a system reboot.....using a USB3 hub resolved my problem.

What is the make & model of this external drive? It is possible this external drive has a hardware problem which is causing it to go offline.

Do you have access to another Mac which you can use to test this drive's behavior?

FYI, you should consider having more than one backup drive. Having all your eggs in one basket results in all the eggs getting smashed if that basket is dropped. It is good you are using two different methods for the backups just in case TM ends up having some issue.

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Answer 2

pumbers Author

Level 1

8 points

Jun 26, 2026 7:03 PM in response to HWTech

The drive is a Seagate 2Tb Backup Slim, and I've tried connecting both via my powered USB 3 hub and directly. It's been working fine on every MacOS version since I bought the machine, and I usually upgrade to the latest version within a few weeks of release, so it's been on every version of Sequoia and Tahoe.

I have three backups - attached 1Tb & 1Tb Time Machine, a 4Tb NAS on my local network, and off-site backups via Dropbox.

I've changed the accessories setting, so let's see how that goes.

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