It sounds like your sync process can create files, but not rename them afterwards.
That long filename you've got now is likely the temporary name you get while the file is being transferred, once it's fully there it usually gets renamed to what you want it to be.
Go up one level and check the permissions for the directory the files are in. The permissions should be read-write, otherwise it'd not be able to create files in there at all, but check if the "sticky bit" is set. That stops processes from renaming files once they are made.
Unfortunately I'm travelling at the moment, but hopefully your file manager will have a way of showing if the "sticky bit" is set for that directory.