Honestly, it sounds like a caching issue, where the browser is showing you a cached page and not the latest. I also know from other websites I have visited and talked with their administrator that there are also settings on the website that can control how often a page is refreshed. Below is the person's reply about setting on their website. Thought it may have some relevance to what you are seeing.
"To reduce the amount automated page calls which were being done throughout the day (tens of thousands), I recently changed the process to check for recent forum replies every 5 minutes, instead of every 30 seconds. The home page has a timer which runs ever 5 minutes to check to see if something has been posted to the tab which you're currently viewing and, if something new is found, the Image icon changes to flashing red. If you then click on that Image icon, the tab is refreshed without having to refresh the entire page.
So, it just takes a little longer for the thing to flash if someone posts a forum reply.
Additionally, the home page does not have (and hasn't) an overall automatic "refresh" so page content will not be refreshed unless you press the browser refresh button or the refresh icon Image/Image above the content tabs."