unable to copy files from "sync" folder to router?

Hello,
a strange issue
using windows 10 winbox 3.37 and also a this sync software
https://www.sync.com/

when I try to copy files from the sync folder to the router - it won’t let me
other places I can copy to
when I copy the folder to my desktop - I can copy files to the router
anyone else have this problem?

I have found this
http://forum.mikrotik.com/t/cant-upload-any-file-to-mikrotik-router/140958/1
but this is a one time solution , I can’t copy the folder each time I want to update the routers
** I have this problem only for Mikrotik routers
Thanks,