OS X El Capitan. 2013 Mac Pro.
When I open a PSD directly from finder into PS I can edit and save the file with no problem.
When I open a PSD directly from LR into PS I can only save it as copy.
Files are coming from an external Synology NAS system.
It would appear to be a permissions problem on your destination folder.
Using Finder or Explorer, go to your destination folder and make sure you have read and write access to it.
Retrieving data ...