25 week pre natal appointment

Hayley • 23.. Happily Taken.. Twin Boys Due 12/25/19💙💙

Hi I had my 25 week appointment today. pregnant with di/di twin boys and when she was trying to find the heartbeats she found the one right away then had trouble finding the other. Ended up going to have ultrasound and she found both heartbeats. Was just wandering if anyone else has or had this issue?