Copy Files step limit?
 

I have been converting our dos command xcopy steps to use the built in Copy Files step. However, I have found that on very large copies (~3GB, 35K files, 4500 directories) it fails after a while with an error saying it cannot copy a file. When I try to rerun it, it fails sometimes on that file, other times on other files. I had to go back to the dos command xcopy to get it work.

I can provide a sample zip but it will be quite large to truly reproduce the issue.

What's the error message? The Copy Files action uses the Win32 CopyFileEx API, and if that returns failure, the action will treat it as such.