Ultrasound Gender Being Wrong

Has anyone ever heard of an 20 week ultrasound being wrong about the gender of baby?

Baby was spine to spine with me and the tech said he didn’t get a clear look but was pretty confident it was a boy .... I was SO sure it was a girl because this pregnancy has been the complete opposite of the pregnancy with my son!

I have another ultrasound in two weeks so I’m going to get them to confirm ... just wondering if anyone has ever been given wrong ultrasound results?