Old threads not working

I often see experienced users direct others to the search function, especially for basic questions. However, that has been problematic for me for over a year. Whenever I try to access an old thread I can see 2-5 posts (depending on the length of each post), and the top of the thread duplicates what would normally be at the top of the site (M4C logo, my username, settings, etc.)

This happens in Safari, Chrome, Firefox, both on Mac and iPhone.

Any fixes for this, or reasons why it happens? Again, it only happens to older threads, some of which are only a few months old.