The "block received for terminated file copy" message is an informational message and can be ignored. Newer versions of SureSync attempt to suppress this message.
The message indicates that there was some kind of a connection issue and SureSync received a block for an old terminated file copy. There are likely other messages in the Job Log for that execution of the Job related to path losses and recoveries.
As long as the path(s) recovered and processing continued, there is nothing to be concerned about.