As shown in the attached screenshot, when clicking on "Browse error log..." button, the application navigates to the file where a list of problemantic SQL queries are displayed.
In order to see the actual error messages a user has to double click on the import task name (marked with red color). This is quite unintuitive. I didn't know I could double click. I searched everywhere where to see the error logs, but it happened to be the double click.
So, to make it clear for a user, please add "View failed queries" button for every failed import task.