Happened to me regarding the Herrington Biography too, there's one paragraph or line of text that's causing it, if you can suss it out and delete it then you'll be fine, look for anything relating to World Wars or other tragedy, for me I just had to remove something about WW1 and Death and Destruction and I was good to go, hopefully you find what you're looking for.
I'd recommend copying the entire thread somewhere else and then posting it in, bit by bit, until you eventually copy and paste the thing causing the issue, then allowing you to delete it