Something new to report.
Tonight, I tried to copy, via Caja, around 3.5 GB spread over about 10 video files from an internal hard drive to an external usb. It locked about a third of the way through the operation. repeated attempts produced the same outcome
This is after installing the fix.
I have not had time to investigate further as I had to go out and willnpt be back at my machine till in the morning. So, I cannot currently say if this is related to the fix, in spite of the fix, or an unrelated issue with the files themselves or, even, the USB. But, thought I should mention it.