Server network share between Mac and PC

I don't think the issue is the sync, I think it may be more to do with how the mac "maps" the drive.

When you create that file on the PC, and look for it on another PC is it there?

Are you absolutely sure that you are looking in the right place on the Mac? My users here have similar issues to what you are describing, and about 90% of the time it's that they aren't looking in the right place.

On the Mac, check the \Volumes\ folder for the file in question by manually browsing to it. Either via the CLI, or using the "Go to Folder" option on the "Go" menu in finder.