Mask in After Effects v 2020 is not accurate I've made sure it's a mask and not a shape layer.  I've precomposed the layer just in case because I&quot;ve applied keylight.  There is no mask expansion applied.  Please help.  Thank you.
Issues like these usually arise when you either have the layer transformed in 3D-space, or when using distortions and transform-effects on the layer. Since you do not have the 3D-checkbox ticked, I assume that you have some sort of transformation applied in the effect-controls. Did you use something like cc-lens, mesh-warp or turbulent displace? If so, first mask the layer, then precompose it, then apply the warping to it.