Ultrasound mix ups

Has anyone had a bad experience with an ultrasound tech? Where they’ve measured sizes wrong? Two weeks ago I had my 20 weeks growth scan which took about an hour and a half. She was very thorough and explained everything to me as she went both girls were measuring exactly where they should and yesterday I had my first growth ultrasound with my new OB (new OB because of a city move) and she took ten minutes, didn’t speak, and then came back with a doctor and I was told one girl was measuring in the 30th percentile and the other was measuring in the 15th percentile. I’m not a doctor or ultrasound tech so I feel dumb saying I think that she messed up, but I do feel she didn’t do a good job. Is it possible for growth to change that drastically so quickly?