This is the link we used (mentioned here), but shows different info instead of the rank #.
Just in case it's theme related, which theme are you using?
A similar past bug also resulted in the thread menu titles disappearing. Can you see the menu titles such as 'Thread Tools' as shown in the following example:
I've had a go at trying various countries with a VPN in case it's a script/bug in ads shown to select countries causing this. I also tried every theme, but had no problem with the thread jumping to the last post.