Nope not really what I wanted to hear, but thanks anyway.

I think I found a solution (at least it seems to work). I mount the shared directory that the file is in. I'm not sure why, but I don't end up with the problem when I do that.

If it turns out I'm just getting lucky, I think I'll end up doing your last solution which is to put an SSH (client and server) on both boxes and transfer them that way.