PostProcess BoxMask-3d objects distorted

i am trying to create a “heat” zone
using PostProcess BoxMask-3D
and in there i am using an UV distortion (“heat” zone)
my issue is: the objects outside the heatzone
are defformed too

as you can see, the cube in front of the heat zone get distorted too
does anyone knows how can i mask it out (or something)
but still show distortion if in heat zone (like the character for example)?