Yes, I do think it is.

HTML made by Claude will, by default, be "sleek, modern", with colorful tables, cards, maybe Tailwind for styling. And, of course it will, if you wanted a barebones HTML, you would just have asked for markdown!

So the LLM decided to present some content using 4 cards, and you now want to add new itens. You can't just add new lines of text: you need to copy the whole HTML of the cards. But the LLM used different colors for each card, so now you have the first cards with varying colors and the new cards all the same color as the last card. Now you have to think about colors... etc etc