Noticed this for awhile but I thought it would sort itself out over time.
I'm finding with a number of groups I regularly grab headers (both in folders and individual) that some, but not all, newly downloaded headers aren't being highlighted green and are instead going straight to 'old'. I usually have 'Hide Old' set and only accidentally found out I was missing seeing some new files. I can't work out whether there's anything specific about the headers that are doing this. Database problem or something else?