[James]

Originally Posted by Jesus.

All of them. Just to give an example of what happens:

Generic 14 page thread exists. I go to last post and it will take me to page 7. I read all the posts to catch up with the whole thread, then I may click on that thread later when it's, say, up to 18 pages, but it drops me back at page 7 again, despite the fact that I've completely caught up with the thread already.

However, it's been completely fine today for reasons that I can't understand.

You don't use the Tapatalk Notifier plugin on Chrome, do you? That keeps you logged in to the forum (I think) and, with Go to New Post, would show older posts that you have already read.

The way Go to New Post works is it goes to the posts in a thread after the Last Visited time at the top-right of the forum.