I saw this problem in 6.0 and in 6.0b1: when I load a GoG and Download Latest, eventually the header downloads in the download list clear and I think the post list is up to date. In V5 there would still be a progress bar at the bottom of the post list showing that it was actually still doing "something", so I'd wait for that. (In fact, I found that even after that, often only a fraction of posts would actually be shown, so I'd do another Download Latest on the Gog and they would all magically appear.)
In V6, I got burned by waiting until I couldn't see a progress bar, re-sorting the list, browsing and adding downloads until after a point in the listing I knew there was nothing more I wanted, then Ctrl-A Del to delete the posts. What I didn't realise was that NewsBin had sneakily been adding more new posts to the bottom of the list in the background, and I ended up deleting them without ever seeing them!
On closer inspection, even after I think the update is complete (no obvious progress bar), I'm actually still seeing the progress bar flicker momentarily on from time to time (blink and you miss it), and I can hear disk activity.
How can I tell when it's REALLY done updating? I've tried using V6 with the Background Updates both enabled and disabled.