Has anyone had inaccurate ultra sound at 15 weeks?

I had a 3D ultra sound at 15 weeks and thought by a 3D u/s ill know babies gender for sure, but the u/s tech said they are not allowed to determine gender by a 3D because da parts look da same and its hard to tell cuz da color makes it all look squishy, so she did a 2D and told me its hard to tell da gender cuz baby is so tiny but she said 80% girl, and told me to recheck when im 20 weeks. Should i believ its a girl by 80% at 15 weeks? Has anyone had inaccurate results