@BassiAoC, many thanks for the response, it’s very informative!
On Bukhara, I reported this a while ago: Bukhara on hard: Hun Raiders suddenly resign. I only played it once and I didn’t make a recording, but someone on YouTube had the same issue (https://www.youtube.com/watch?v=hbuQsUrYFxc at 6:30).
A few months ago I had played the same scenario on Standard and the Hun Raiders didn’t resign, so it does seem to be a problem only with Hard difficulty.