Hi all — I know NIPT is super accurate, but has anyone had theirs say low risk and it ended up being wrong?

Backstory: I went for my 20-week scan yesterday & baby’s femur length is measuring small. They took multiple measurements but baby wasn’t cooperative & they used the smallest one for the report. Sonographer isn’t super concerned since I’m short, but she said it can be an indicator for Downs. My NIPT came back low risk (and I had low PAPP-A in my last pregnancy — this time wasn’t tested). I have another scan next week with specialists. I’m not panicked or anything, but just didn’t know if NIPT was wrong for people.