17weeks ultrasound

Question pwede ba mamali ang ultrasound? I had my gender check ultrasound on my 17weeks actually naka twice kami kasi una di tlga makita then the other day bumalik ako baka raw makita na on my first salang wala di pa din makita then pinatayo ako at pinaglakad lakad tapos inom cold water para gumalaw then salang na ulit medyo hirap makita, then later on my ob says it's a girl raw pero my husband still doubt about the gender baka di pa sure un nakita ng doctor. Haay kasi super excited lang ako malaman gender. Anyone may scenario ba kayo namali sa ultrasound?