Having a camera pointed at you and recording can really mess with a person’s head. This is a fairly common issue, even among people who don’t deal with stuttering. Something about the pressure to perform and not make mistakes somehow has the opposite effect on a lot of people. I experience this myself on the regular. One way to overcome this is through “exposure therapy”. Get lots of practice and exposure to the thing that makes you most uncomfortable, and it will slowly begin to normalize and lose its power.