Feel free to edit the title to explain better what I am going to write here.

When I copy big files to a pen drive for example, the progress window shows an estimate that most of the time does not fail to show the real time and percent to finish, but there are cases where it says everything is finished and the progress window closes. I go to extract the pen drive and it says it is still in use. After checking the pen drive I see it is still copying the files but there is no progress window showing this.

It does not only happen with big files, it also happens with many small files. If I copy them, the progress bar might say 15 seconds for example and finish in that time, but the real time might be 1 minute and for the next 45 seconds I need to actually look at the light in the pen drive to see if there is real activity on it.

I do not want to know how to fix it since I have read how deep a fix for this could go. What I want to know is why does then the progress window show an estimate that does not correspond with the process of copying.

Is it dependent of the Cache in the external unit?

Is the file size and amount of file influence on the correct estimation. For example 1 file of 4 GB or 1000 files of 4 MB.

Is there configuration options that can change the behavior.

There are other questions similar to this like copying files to usb stick never finished but am more focus on the mechanics into why it would behave like this.