This has happened to me a regularly.
I use the New Posts function. Scrolling down, I see a new post for a thread and click on it and usually see the post. However, sometimes, I see a post and can't get to it to read it. The click on the last post button takes me to the first post.
The current example is the Shrimp vs. prawns thread. The new posts listing shows a post from Jennyema. I can't pull it up. There is a page 1 of 2 icon but clicking on page 2 takes me to page one.
If I select jennyema's name and click on "show all posts..." I can see the begfinning of it but can't get it to display.
Something is stuck and needs a squirt of oil to loosen it up.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan