Comment by alistairSH

From what I'm reading in other comments, the problem was Claude1 got increasingly "frustrated" with Claude2's inability to do whatever the human was asking, and started breaking it's own rules (using ALL CAPS).

Sort of like MS's old chatbot that turned into a Nazi overnight, but this time with one agent simply getting tired of the other agent's lack of progress (for some definition of progress - I'm still not entirely sure what the author was feeding into Claude1 alongside errors from Claude2).