How to get more details about skipped files during backup?

I did a few test backups and the logs seem alright except:

*06:04:22.662 3 directories and 10 files were not included due to access errors
*

as I am left wondering what exactly was skipped. I tested on Windows, running scheduled and as a service using VSS snapshots so why would it skip?

For each directory or file not included, you will find a log message near the beginning of the log file that explains why it was not included, most likely due to permission issues.