SAMBA has crashed after I’ve allowed a great deal of small files to be accessed through a windows share (.hpp files from boost; I have a number of boost versions stored on MyCloud device - and that is a lot of files!) - I was building something many times, so a million file accesses or more could easily have occured ( over an hour? half an hour? few minutes? hard to say :/).
Restarting samba using the ssh (/etc/init.d/samba restart) worked fine.
Apple sharing through afpd was unaffected (it worked when samba was crashed).
What is the quickest way to diagnose the problem next time it occurs? Small file access is somehow quite slow so I will probably migrate things back to the local hard drive.