Another confirmation ultrasound?!?

So I had my anatomy at 18 weeks baby was measuring 17weeks my baby was so stubborn I’m breech position my 30min ultrasound turned into 1hr they had a hard time getting measurements but they got them they told me his legs was crossed whole time and I believe that he is a lil a boy it will be my third son however they said they want me to get another ultrasound because the shots that they did get looked way different from each other as they were taken from same angle .. had this ever happened to anybody else my next ultrasound is the 2nd!