Video recording twice

[Zipster]

Hi when I press record on the handset it records but it records twice first 1 a little jerky and the second is pretty perfect, is it something I'm doing wrong or do I just delete the jerky 1 every time thanks in advance for any help, just 1 more thing when I put my galaxy s8 in the holder it always seems to be pushing 1 of the buttons on the side of the phone and if I move the phone then it pushes 1 on the other side