Mark All Read - Not Working

The "Mark All Read" button doesn't seem to be working corrrectly

This is what I did:

A) Click Threads -> All Threads -> Subscribed Threads.

The following screenshot appears.

B) I then click the "Mark All Read" button and get the following screenshot which is as expected.

C) I then click Home -> Threads -> All Threads -> Subscribed Threads and the 2 original threads marked as having unread posts have the original blue/white icon next to them indicating unread posts even though I clicked "Mark All Read" in step B. See screenshot below.

Unfortunately "Mark All Read" is very, very slow or not working properly.

My op in this thread was over an hour ago and I took this screenshot about 1 minute before this post.

The 2 threads are still the same, indicating unread posts even though I clicked "Mark All Read" over an hour ago.