It is just this thread that is a problem. There is a # in the thread title. The # symbol is used in URLs to indicate where within a page to link to.

The BBS uses that to link to the first new posts within threads when viewing in flat mode. The BBS clearly doesn't do quite the right thing when constructing this links to the new posts. It should do a thing called encoding, that replaces special characters like # that have special meanings.

Because it doesn't do it correctly the link to the first new post for this thread doesn't work.