Catalina - External Hard Drives repeatedly ejected without cause.

I am uninstalling software that is no longer compatible with Catalina that I don’t use as I need the IMac to work properly.

10.15.4? Seems that has caused more problems than it fixed.

Nice thing about TM is that you can Restore everything back to where it was working better.

Do you have any usb powered hubs? I found this to be an issue with mine. I thought it was WD software that I removed but it seems to be the usb powered memory card hub I had plugged in.

Does the machine still eject the drives, if you disable automatic sleeping?

You don't need to revert the computer. You can install it on an external drive and boot with that drive. for what it is worth, part of my backup system is a current clone of my internal drive. When I upgrade to a new OS I keep that clone so I can boot with the older OS should I discover a software or hardware issue associated with the new OS.

Same problem for me, but my drives are various USB 3.0. Random ejects, sometimes folders hang whilst loading, then the eject occurs.

Also my old partitioned  Lacie, 2TB for Time Machine, 1TB drag and drop items, locks up randomly when coping files from either partition. The 1TB partition is currently dead now. Disc utility cannot fix the partition.

I suspect Catalina also.

Disabling "Put hard disks to sleep when possible" in Energy settings seems to have fixed it over the last hour. Definitely an OS issue. There's been a few bugs i've come across in Catalina that really has me scratching my head.

I have a 2013 Mac Pro and a Lacie 2big Thunderbolt 2 RAID array that, after installing the 10.15.5 update, will not mount. I am worried that I have lost around 40,000 RAW files. The level of rot that has set into Apple's macOS releases is just astounding. I've been a Mac user since the days of the SE, but the steadily eroding quality of their software has me seriously considering alternatives. The hardware continues to be mostly good, but the software is now of the quality that we mocked Microsoft for in the late '90s and early 2000s. How can a company with the resources of Apple release such shoddy software?

I'm a video producer - I'm having a parallel issue. I use a 6tb LaCie d2 pro drive attached by thunderbolt to my iMac Pro. I have had zero issues until installing the 10.15.5 Catalina update.

Since then the drive disconnects constantly.

Reconnect the drive to a MacBook Pro that is still running Mojave and the problem disappears. No suggested fixes seem to work.

Irritating that I forked out for an iMac Pro only to have it borked by an update and have to resort to doing client work at a snail's pace on a 2014 laptop.

Exactly the same issue here. Bought a new Lacie 8TB Thunderbolt drive, connected via USB cable. Was working beautifully for a week until I upgraded to Catalina this weekend. Now it ejects at random intervals during the day. Have tried all suggestions except reverting back to Mohave. As this is affecting other people, it does appear to be an issue with Catalina. Please would support at Apple respond? Thanks.

I was informed its a catalina only issue with drives connected to thunderbolt ports. I reformatted it and ran all suggested checks to no avail, hence returned as unfit for purpose, as it would randomly disconnect requiring reboot each time to bring online.... useless, and apparently the latest ios updated hasnt fixed the issue, so holding back buying another make (lacie support was way too slow to recommend)

Not tried a Big Sur Beta, but I'm not one for trying betas - I tend to wait a good long while to update the OS so most bugs are squashed.

I’ve erased then reformatted the drive to APFS and copied across all my data. Whilst the data transferred, the disk stayed mounted. However, the disk ejected once it was not being used for a while.

Obviously it is Catalina that is the issue. HOWEVER.... it is odd how my the other older Lacie drives are working fine with it though. Anyone have any other suggestions?

What solved my problem was to put my external USB SSD on a thunderbolt connection to my Mac Pro (Catalina) via the thunderbolt display. Once I installed the Big Sur public beta, I moved it back to a USB port on the Mac Pro directly and the problem has so far not come back. 2 days and counting.

I'd also like to know when this will be addressed. I used to have this problem on my older tower after I had upgraded the PCI card. Chalked it up to an external piece that made it glitchy. Flash forward to getting my new trash can Mac a year ago. All ran smoothly with multiple external drives attached via USB until I upgraded to Mojave. Started getting the External Hard Drive eject message after waking from sleep — frustrating but hadn't altered productivity.

Now, since upgrading to Catalina, it's not only giving me the same messages nightly (even though the drives are still clearly connected), it's also hiccuping the connection during the day. I work off an external drive and keep various folders open for different jobs. When navigating back to an open folder, I'll notice that all folders have closed except one and that one is back to the root level of hard drives.

As of today, the connection disrupted my file saving. I went to save and there was no path to the file anymore. I was prompted to save with a different file name to keep working. One version ended up corrupted. Luckily, I was able to go back to an earlier version and make only minimal edits to bring me back to where I was. But this is extremely frustrating and worrisome.

I'm running Catalina v 10.15.6 (19G2021) on a late 2013 Mac Pro with 3 GHz 8-Core Intel Xeon E5 processor. I made sure the system was updated as of 2 days ago and I did reset the SMC as suggested either earlier here or on another similar thread — to no avail.

ETA: I realize this thread was filed under iMac's, however, it appears to be an OS issue, not tied to any one hardware.

yes I also was to quick disabling boot protection did NOT solve the problem, Thunderbolt 2 HD with adapter as well as USB 3 HD's still eject... so forced now to sell all my "old" HD's and move the Thunderbolt 3 as that seems to be the only thing which works with Apple nowadays