So I have done a ton of reading lately. Mostly to get one of my badges. The other part is stress relief and mind diversion form work. Plus to build and boost my knowledge. But since then the unread list /new / latest doesn’t update accurately. Occasionally I see that the notifications don’t update either. I do 95% of my Acivity on my cell phone (Apple)
I did clear my history cookies and cache on my browser.
Is it a “I did too much in the last week” deal or am I crazy (probably I know) or hmmm?
I’ve had a problem where if I go to a post and go back the list is all funky, but a page refresh usually fixes it. Also, there’s some settings in your preferences toward the bottom of the page that change how often you will get notified of things and what the forum will consider “new” for you. At the bottom of every post there’s a button that says either “Watching” “Tracking” “Normal” or “Mute” and that will also control whether you get notified about a topic or it shows up as ‘new’ in your feed.
Hope that helps. If not, let me know and maybe we can figure it out. 
It’s more of a wonder. I’ve noticed “new” threads that I haven’t seen. But it’s ok.
That happens to me only if I have muted a topic/thread. The notification will show but not the actual thread or update.