What is up with "you last visited" indicator?

This is probably going to sound terribly unclear, but here goes:

Lately, it seems that the site isn’t updating the “you last visited” thing when I pull it up. This, of course, affects the “new posts” icon when perusing a given forum. The only way to update the “last visited” thing is to click on “Mark All Forums Read” on the SDMB main page.

This isn’t the way it normally works. Normally, it shows the last time I pulled up the SDMB, i.e., if I look at forums at 8:00, 8:30, and 9:00, when I look at 9 it shows 8:30 as my last visit. The way it’s working now is that when I look at 9 it shows 8 as my last visit (assuming 8 was the last time I “marked all forums read”).

It’s kind of irritating, because I’m basically stuck between choosing to display more threads as having new posts than there actually are, or showing no threads as having new posts.

So what’s the scoop? Is anyone else having this happen?

I never use those indicators and never tried to take the time to figure out how exactly they are supposed to work. But I will make a special effort to learn over the next few days. In the meantime, perhaps someone who does have an idea of what they are supposed to do can provide some insight.