Nah I think its pretty common doc couldn't get my baby to cooperate either so I have to have another ultrasound in a couple weeks.
I had the same thing except with mine they couldn't measure her heart, she was blocking evrything. Babies aren't very cooperative in there lol. I wouldn't worry.
It happened to me in my last pregnancy. The ultrasound tech even told me my doctor might need to order a new a new one because she couldn't get a good pic of the spine. It all depends on the position of the baby and whether or not the tech can get all the pics they need. Sometimes the baby just doesn't want to cooperate:)
Same thing happened to me but everything was fine! Plus you get to see and have more pics of baby!!
Ires very possible baby just wasn't cooperating. You can always talk to your doctor about your concerns too, but I wouldn't be too worried it. They would tell you if there were something wrong.