Opinions Please

I’m currently 14 weeks pregnant with 3rd baby. We decided to do the nipt test around 11 weeks (first time doing test) but they messed up the first 2 tubes and had to use another set of tubes. Also a man drew my blood and I also had my 3 year old son with me. I’ve read that in order to do the blood test and get accurate results is from staying away from men and cleaning everything before you do it or they can pick up the Y chromosome from the men. And that also a Y chromosome can be picked up from previous pregnancy. I know some women who’ve had it done and got false boy tests and actually ended up having girls. But our test came back as a boy and something is telling me it’s wrong. We have a soon to be 9 year old boy and a 3 year old boy. I knew they were boys without confirming on the anatomy scan but with this baby I’ve had a feeling it’s a girl. Anyone experience false Boy tests?