The screenshot script is the scarier half of that story, because the seven failing tests did their job while the previews kept coming out at 40% and looked like work getting done. I had a similar situation, the engine landed on a screen that looked almost like the expected end state and reported a pass, and it took a person going through the step screenshots by hand to notice. Did measuring inside the frame fix it for good, or you need to check the previews as well?