Question about Tale of the Dragon campaign

I just downloaded the Tale of the Dragon expansion from Steam, and I keep running into an issue in the first chapter of the campaign (Rising Waters). Every time I play it, I get a "You are defeated!" popup seemingly randomly. I'm not being attacked, I haven't lost any crucial characters, and everything seems to be going as normal. It happens different times each time I play (once it happened within a couple minutes of starting, the next time took about 20 minutes, etc.). It's always before the first flood countdown ends. Googling it hasn't given me the answer I'm looking for, namely why do I keep losing the scenario?

My computer has some issues, so I'm trying to pinpoint if it's an issue with my computer or if there's something I'm missing in the campaign. Help would be greatly appreciated!!