The "Details" message section is dependant on the action the client(s) is/are taking. Not all actions will have details.
For instance - you might have a
MESSAGE -- DOwnloading file
DETAILS -- File 5 out of 621 -- downloaded 21%
type message ... or a
MESSAGE - INSTALLING PACKAGE
Details -- NONE
... because the installer is doing its thing and we're waiting on the client telling it what to present on the console. So not EVERYTHING will have a DETAILS section to mention.
If you need detailed information on what's happening on a particular client, you'll want to look at the vulscan log.
If patches fail to install, we'll tell you at the end of the current job (1 may fail, but we may have to try 20 others to install, for instance).