Copying files from remote side failed - PERMISSION DENIED on read-only connection

Hello there. I frequently find my WinSCP sync scripts fail with the error below. I can't understand why there are permission issues on certain files...can you recommend any troubleshooting tips? Excerpts from log below. Thanks!

. 2016-01-20 01:30:34.519 --------------------------------------------------------------------------
. 2016-01-20 01:30:34.519 WinSCP Version 5.7.6 (Build 5874) (OS 6.1.7601 Service Pack 1 - Windows 7 Enterprise)
. 2016-01-20 01:30:34.519 Configuration: D:\FTPBolivar\WinSCP.ini
. 2016-01-20 01:30:34.520 Log level: Normal
. 2016-01-20 01:30:34.520 Local account: MVD\B3ECHDKR
. 2016-01-20 01:30:34.520 Working directory: D:\FTPBolivar
. 2016-01-20 01:30:34.520 Process ID: 9460
. 2016-01-20 01:30:34.520 Command-line: winscp.exe /console /script=SynchronizeFTP.txt /log="D:\FTPBolivar\FTP_LOG.log" /loglevel=0
...
...
. 2016-01-20 02:17:53.193 Asking user:
. 2016-01-20 02:17:53.193 Error transferring file '/Contract Specifications/14-C-0003 Specs Awarded Certified Final with Attachments.pdf'. ("Copying files from remote side failed.","Permission denied.")
< 2016-01-20 02:17:53.193 Script: Error transferring file '/Contract Specifications/14-C-0003 Specs Awarded Certified Final with Attachments.pdf'.
< 2016-01-20 02:17:53.193 Script: Copying files from remote side failed.

< 2016-01-20 02:17:53.193 Permission denied.
* 2016-01-20 02:17:53.193 (EScpSkipFile) Error transferring file '/Contract Specifications/14-C-0003 Specs Awarded Certified Final with Attachments.pdf'.
* 2016-01-20 02:17:53.193 Copying files from remote side failed.
* 2016-01-20 02:17:53.193 Permission denied.
. 2016-01-20 02:17:53.198 Script: Failed
. 2016-01-20 02:17:53.198 Script: Exit code: 1
. 2016-01-20 02:17:53.200 Disconnected from server

Is it the same file(s) each time? Or is it random? Does it succeed on retry?