Unread Posts Do Not Update

[AU Doc]

The browsers on my Apple devices do not show that I've read posts until hours later. That is, I can read all of the new posts in a thread, and the next time I visit the site it will still show as having unread posts. It usually takes several hours (sometimes most of the day) before the threads are marked as read.

Is this a normal behavior? I have seen this on my MacBook, my iMac, an iPad, and my iPhone. I don't have a PC to test, and I haven't tried with Chrome or other browsers.