This issue has been added to the tracker:
https://winscp.net/tracker/1355

OK, I've investigated the log anyway, only to confirm that your system behaves inconsistently. The API call for the same file returns different results each time. There were no errors because the calls that fails is done for logging only. And the later call that's actually used for error-detection does not indicate any error anymore.
So it's looks like either bug in the system or some driver.

Socko71 wrote:

Ran a long time and timed out on connections but does show where it failed on copies

Thanks. Though there's no "A call to an OS function failed" error.

martin wrote:

OK, if you do not mind, one more time...

Ran a long time and timed out on connections but does show where it failed on copies

OK, if you do not mind, one more time...

martin wrote:

Thanks. It behaves really strange. It seems that accessing the affected file fails only once. When trying the same operation immediately after, it succeeds.
I'm sending you yet another build to confirm this.

sending 2 files log and trace...I ran it until I got 3 errors before aborting

Thanks. It behaves really strange. It seems that accessing the affected file fails only once. When trying the same operation immediately after, it succeeds.
I'm sending you yet another build to confirm this.

martin wrote:

Please one more time.

Thanks for putting your time into this issue

Please one more time.

martin wrote:

Thanks. I'm sending you a new debug build.

Sending 2 new files using latest debug winscp

Thanks

Thanks. I'm sending you a new debug build.

martin wrote:

Thanks for your report.
I have sent you an email with a debug version of WinSCP to address you have used to register on this forum.

Thanks I ran the debug version and included the log file and trace file. Is that all you needed?

Thanks for your report.
I have sent you an email with a debug version of WinSCP to address you have used to register on this forum.

When using commandline. scripts or Commander when I try to upload data to a remote server from a Window 2008 server that uses data deduplication I get the error (EOSError) A call to an OS function failed a various files through the tranafer until I abort it. Yet I can copy the exact set of files and folders to a 2003 server that doesn't have data deduplication and it transfers the files with no problem at all. I included 2 files label 2003 and 2008 of the transfers. I aborted the 2008 after a few errors.