Repro steps:
1) Open the project and import the RaycastBugUV.unitypackage
2) Add a Mesh Collider to the plane object
3) Select the plane object and set Step variable in the Raycast Test(Script) component to 0.1
4) Click Generate Texture
5) Notice that there is a small part of the generated texture missing(user attached screenshot shows the missing part)

N.B. To get correct texture generated you need to set Step variable to 0.005, which then takes ages to generate the texture and it makes the Editor not respond while generating