Error code 100092 when trying to copy a file to a Toshiba external drive

I get this error message when attempting to copy to a Toshiba External 2 TB HD formatted APFS: The operation can’t be completed because an unexpected error occurred (error code 100092). This is a new problem, as I bought this drive about two weeks ago as a backup drive and copied 1.3 TB of files to it, and I believe I have copied files to it up until just recently. I have done a search and tried most, if not all, of the suggested troubleshooting tips, except reformatting, which I guess I will have to do if nothing else works. I have to back up 1.3 TB first, which will take about 9 hours. Also, I get this error message when trying to copy a file to the Toshiba on my Mac Studio and on a Mac Mini (Intel). This would seem to indicate the problem is with the Toshiba (and I can copy to other external drives).

Steps to resolve Error Code 100092 not necessarily in this order

1. Updated my Mac

2. Restarted

3. Ran Disk Utility's First Aid on both the Mac HD and the external drive.

4. Booted into Safe Mode. Still could not copy any files and got the message.

5. Checked File Permissions. I gave Read and Write permission to everything listed.

6. There was a suggestion to go to Get Info -> Sharing and Permissions and check Ignore Ownership on this Volume. It was already checked so I unchecked it and then rechecked it.

7. Relaunched Finder

8. There was a suggestion to delete the .DS_Store using the command sudo find / -name .DS_Store -delete, but everything came up as "operation not permitted".

9. There was a suggestion to run fsck, but I was not able to boot into single-user mode.

After I rebooted into my usual user account with the Toshiba still attached, I could move the cursor/arrow, but nothing happened when I clicked or double-clicked on anything. Rebooted again and unplugged the Toshiba drive, and everything was back to normal (except, of course, the problem I am writing about).