Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
I've been dealing with this maddening and probably data-dangerous issue for a long time. I've gone down the rabbit hole more often than I care to remember and each time hit a dead end. I submit that it is not:
  • A Mac model problem (I have an Intel i7 mini, and it's been reported with Apple silicon, including at M2 Ultra Studio)
  • A Mac OS version problem (I've lost track of the upgrade-will-solve-it prayers over the years. Still happening in Sonoma 14.4)
  • Solvable going to a powered hub (Happens with my SOTA CalDigit powered TB hub)
  • Solvable with an energy/sleep setting change (Tried them all)
  • Solvable by plugging the external volume directly into the computer (Just happened before my eyes)
  • Unique to any one drive manufacturer or type (Happens with my GTech and Samsung, one an HD and the other an SSD)
I believe this problem has been carried forward by Apple across models and OS versions. Chained ports in particular are so unstable that my iPhone, plugged into the back of my Mac-specific LG monitor, doesn't stay mounted long enough to transfer photos. They must know because innumerable reports have been submitted and the Internet is yelling about it.

Is there some app/utility/extension that every one of us is using that's creating this issue? Doubtful. I'm open to hope but at this point I think it's simply unsolvable, or at least too complex for a universal fix to be in the offing. Somebody please prove me wrong.

EDIT: It just happened at startup. My "solution" will be to buy a Mac with a really large internal drive and use my Synology NAS, with which my Mac can play just fine, for external volume needs. I no longer see the value in lots of ports when they can't be relied on. Sad but, at least in my case, true.
 
Last edited:
  • Like
Reactions: Farrol and gradi
Earlier in this thread somebody recommended the app, Amphetamine. That solved this maddening issue for me. Good luck!

<<Is there some app/utility/extension that every one of us is using that's creating this issue? Doubtful.>>

For me, the problem only occurred when using Premiere Pro.
 
I have posted here and elsewhere, that this INSANE dismounting issue for me has been resolved by installing Amphetamine. I'm still surprised this bandaid is required after all this time!
 
I have posted here and elsewhere, that this INSANE dismounting issue for me has been resolved by installing Amphetamine. I'm still surprised this bandaid is required after all this time!
Yeah, saw that. Interesting. I might give it a whirl. No biggie with a desktop machine. Do you recommend any specific settings? I assume this wouldn't be app-specific, unless we’re talking about the Finder. Thanks.
 
OK, was doing fine, no events overnight. The mini is connected via Ethernet, and I wanted to use Airdrop so I turned on Wifi (which I had off). Instantly the external drive dropped and the error window came up. Any networking geniuses out there able to tie these things together?
 
OK, was doing fine, no events overnight. The mini is connected via Ethernet, and I wanted to use Airdrop so I turned on Wifi (which I had off). Instantly the external drive dropped and the error window came up. Any networking geniuses out there able to tie these things together?
Interesting… Maybe the reverse:

 
I eventually decided to use Amphetamine and that has solved the problem. The only problem is that the drives stay on, but since these are NAS drives I'm okay with that. :/
 
Hello, thought I'd chime in. Same issue with El capitan-mojove 2014-2018, and two western digital usb drives, And random usb sticks dismounting by themselves with notifications saying so.
Got a hub, both WD usb are power plugs run natively, so not a usb port power issue.
Apple store had to fix the silent recall on the 500 fire pro card defects detected when bought, but didn't offer, letting the warrenty run out, not wanting to fix, but forced when getting certified apple tech in house at my expense, to witness and address no boot pink screen, usb drops...And said the riser port card wasn't seated correctly, causing dropped usb devices. They changed one of the fire pro video cards to a 700, leaving a miss match...USB devices still get dropped on mojave. So I'm thinking a stab back to MS and USB, for their drop of Firewire/thunderbolt 1-2. I've now read MS is unfare to AMD cpu's...in some finding intel cpu's falsely bench mark practices...So, we as *consumers* get a constant pay to fix/bug hunt, pay to do rnd for free.....Seems a side to spy n lie...underhandedly getting depended on...Be careful to not become too reliant on these things...and tend more to the living Good...maybe is good uttered counsel.. regards. But finding others having issues....and they think AI will run us better?...lol...the delusional dream many think tech will save the day....until oops.
 
This thread started in early 2022 and all you've mentioned above is STILL happening now in March, 2025. My recently purchased 2023 Apple M3 iMac running Sequoia, OS 15.3.2. Not only that, but the new iMacs are eliminating all but 2 or 4 USBC ports. Mine only has two ports (wish I'd shopped better). Not only that but the iMac itself has an EXTERNAL power supply. All of that means a huge increase in cables and desktop clutter because I've had to buy two new docks to accommodate it all. By the time you're tacking on extra docks, hubs and adapters, I'm not surprised that we're facing this stuff even today.
 
ITS 2025, im on a M3 air 16gb with 256gb SSD, bought a thunderbolt 3 external 4tb SSD to use for all my my editing. Have had this issue for months now, tried other cables, drive enclosures, factory reset osx, the only thing that worked for a while was using the 2nd usbc port, but then it came back, tried reseting the ram(?) someting arrather by holding in control + R at startup, online says it will make a beeping noise if it works, didnt for me but the drive stopped unmounting while in use. I've turned off disk sleep mode as the issue came back and I noticed it mostly when the drive is connected overnight it will unmount by the morning.

wondering if this is a software bug, or if its the power sleep setting that unmounts the drive over night when left plugged in, which then makes the drive unstable when it happens a few times.(?)

the drive shows healthy in utility apps, the data is on there, no signs of drive corruption...
I'm about the restart and do the comand + R thing again, hoping for the best.

I've also tried uninstalling osx updates, and even updating to the latest beta updates, seems the problem still is not being addressed for future updates.

maybe apple like this bug, since it means you cant just buy the lowest internal SSD model and plug in a big external through thunderbolt; just spend more on a larger internal... wouldn't put it past them.

I've been on windows my whole life + iphone/ipad pro. so far, my experience with my macbook air has been amazing as far as things just working and not having a computer that crashes all the time and needing driver updates and other BS (windows 10 updates/11) EXCEPT for this one issue.

won't be buying any more apple computers until this issue is resolved.
 
Here is more info on the "reset RAM thing" I mentioned:
If your external USB-C drive keeps unmounting on your MacBook Air, try resetting NVRAM/PRAM (Option-Command-P-R at startup), ensuring all connections are secure, and checking for file system errors using Disk Utility.

Here's a more detailed breakdown:

1. Reset NVRAM/PRAM:
  • Why:
    NVRAM (Non-Volatile Random Access Memory) stores system settings, and resetting it can resolve various issues, including those related to external storage.
  • How:
    • Shut down your MacBook Air.
    • Turn it back on and immediately press and hold Option-Command-P-R.
    • Hold these keys until the Apple logo appears and disappears a few times.
    • Release the keys and let your MacBook Air start up normally.
  • Safe Mode:
    Start your MacBook Air in Safe Mode (Shift key during startup) to see if the issue persists, which can help identify software conflicts.



    LINK TO MORE INFO
 
Apple Support:
The steps to reset NVRAM don't apply to Mac computers with Apple silicon, and aren't needed on those computers.

As pointed out before: a temporary solution answered is to run a sudo command in Terminal to stop the usbd process from running on your Mac:

sudo killall -STOP -c usbd

which pauses the process until you either reboot your Mac or enter

sudo killall -CONT -c usbd

to restart the process. Temporarily this appears to fix the connection issue for most people.



nota bene: the above is not the same as using Activity Monitor to kill the usbd process - because killing it there will just restart it the next time some device is connected via USB to the Mac. But stopping the usbd process using the sudo killall -STOP -c usbdcommand, pauses it until you either reboot your Mac or enter the continue command for the process. When the usbd process has been paused, it won't restart even if the a device has been connected to the Mac via usb.

People have created various solutions to automate this using launch agents/deamons, shell/apllescripts/automator. the simplest approach IMHO is a shell script:

#!/bin/bash
killall -STOP -c usbd


for convenience you can wrap this into a clickable form using e.g. Platypus.

This will obviously not help with e.g. with dirty cable connectors or ports (or cable related issues).
 
I think I've fixed mine after a week of testing one last thing. Since Apple has reduced their USB ports on new iMacs like my M3, I've had to buy two new powered docks for the only two USB C slots on the back of my iMac. Among the things in this growing mess of spaghetti behind the iMac was an old powered USB hub (pre-USB C) that has loyally worked with the two backup drives left plugged into it until I got the new iMac. That old hub was plugged into one of the new docks. All of this daily nasty unmounting of two of my backup drives has ceased after reconfiguring the new Docks to eliminate that old hub. It had worked consistently before I bought the new M3 iMac. In nearly a week, the two drives have yet to be unmounted.

Now all I need to do is figure out what new shorter cables I need to clean up all the spaghetti. Daunting considering that some need adapters and some don't.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.