New posts were placed in the middle of the last page, not appended at the end, as it should be. Also, when I reload the page, the thread stays bolded, as if I had not viewed it.
There hadn't been new posts in a while. What people have historically done is, post a pic, then, after a period of time, take it down, with a replacement text of "poof". Looking at the dates, it doesn't look like posts were lost.
Not being any sort of programmer, I would venture a corrupted thread, also.
I figured out what happened, but not the why. Starting with post #42,264, the post numbers are repeating. @SurfingDoctor figured this out and post padded to get us past the old post numbers. However, we've put in a help desk with the forums software provider to research the issue.