The thing that bothered me the most is that the Lannister-Tarly army was taken by surprise by an ENTIRE Dothraki horde and a big ass dragon. You mean to tell me that Jaime and Randyll didn't have outriders to scout ahead or behind them? Jaime in the books ,after his defeat at the Wispering Wood, adopts a strategy to always use scouts even if he is in friendly territory. Also about the scorpion, the thing that they didn't deploy it earlier didn't bother me, what bothered me was that they had only ONE, so you have created a weapon capable of wounding a dragon and you didn't mass produce it?
I didn't find the right solution from the internet.