The 'probe' is the first step within the automatic (group) based backup process.
It will check ...
  - whether the client is listening for a server request
  - whether this server is allowed to receive the date
  - which save sets will result for the save set 'All'

In your case the backup request is already rejected on the very first step. 
This is most likely due to the fact that the client listener (nsrexecd) is not 
running (any longer) or hung.

The timeout for this process is more controlled by the client retry count.
The inactivity timeout will control the data transfer activity during the 
backup phase later.

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