Cannot Unmount for First Aid Disk Utility

[JayElDee]

Running Monterey 12.6.7 on iMac 5k 27" 2017
There are a few external drives that I cannot address in First aid — to run maintenance scripts for permissions.
I get this error:
Running First Aid on “Transcend 4Tb” (disk8s2)

Checking file system and repairing if necessary and if possible.
Volume could not be unmounted.
Restoring the original state found as mounted.
Unable to unmount volume for repair. : (-69673)

Sometimes I will get a message stating that First aid cannot be run because a file is using the drive I am addressing. AFAIK, there is nothing running.

Sometimes a reboot and a fresh attempt will succeed, sometimes not.
Any help appreciated and TIA

 

[kitKAC]

Boot into macOS Recovery and try running First Aid on the drive from there.

 

[HDFan]

If a drive is being used by an application then it can't be unmounted. One way to check in terminal is:

sudo fs_usage -f "Disk Name"

 

[bogdanw]

It's probably best to follow Apple's advice:
"From the utilities window in macOS Recovery, select Disk Utility and click Continue."
"Choose View > Show All Devices (if available) from the menu bar or toolbar in Disk Utility."
"Repair volumes, then containers, then disks"
https://support.apple.com/en-us/HT210898
https://support.apple.com/HT210898

 

[JayElDee]

Sorry to be just getting back.
I did as @bogdanw suggested. On one of my external backup drives (OWC 14tb) the volume "passed" first aid as did the the container. When I ran first aid on the disk I got an error message:
The partition map needs to be repaired because there is a problem with the EFI system's partition's file system-69766).

This is my newest drive and the problem described predates this drive in my system. It is NOT my boot drive.
Is this anything and how to address it if it is a problem?

 

[Lipaz]

And that’s Apple forums and services everywhere. Vast majority of customers are getting such errors (I have this exact same eith external Crucial SSD) since updating from BigSur.
Apple is not wiing to reveal information about this, and not willing to solve it. Just buy their overpriced fix internal SSD. ) Biggest scam of XXI. century so far, apart from Russian military.

I have HFS+ on this current SSD, by the way. Why? Because it worked just fine on my 2014 laptop SSD, and APFS is not reliable on external storages… if something is wrong, you lost everything, can’t repair it.

 

[HDFan]

Vast majority of customers are getting such errors

Source?