I have found a few "dead" systems recently as well, not only do USS not show up at all, but I usually scan ships while waiting for them to pop and I didn't receive any data from 50 or so ship scans. I then moved to the next Outbreak system where the first USS to pop was an HGE. And I noticed that the only Ship Scan that provides Abnormal Compact Emissions data is a system security Anaconda, but only rarely does it show up, haven't received that type data from any other ship type yet, so I always make it a point now to scan every Anaconda I see, cause I need a lot of those for sensor upgrades.