Camera set up for green screen critical. I’m guess that if it was a sony camera with a standard scene file, the camera might have a bit too much detail enhancement dialed in, which is frequently the case with sony and some other cameras. Unfortunately detail enhancement is the enemy of chroma key in that it frequently adds noise to dark areas, essentially its enhancing the noise and that causes havoc with keying.
Its far better to use a bit less contrasty camera profile and dial the detail wayyy back. On my C 300 typically I have the detail reduced to -10 or so because even at the out of the box detail setting of zero there is far too much enhancement for a pulling an easy key.