Chance sneak peak is wrong?

I got boy result at 8 weeks, at 15 weeks I didn’t see or find out the gender but when they did a measurement I didn’t see anything between the legs (didn’t see specific genitals either though). The place that I go to don’t tell you until 17 weeks minimum. I go for my anatomy scan in 2 weeks.

I have seen some wrong results and I know boy results happen more frequently because of contamination but also since read if you have a boy under 2 it could affect results? Is this true? My son was 12 months when I took the test.