Help with PlaymatMask.png

I wanted to change the mat, so I copied my image into YGO Omega_Data\Files\Playmat , and it worked perfectly.

My problem is the mask, I have changed the file PlaymatMask.png to a plain white in the Textures\Field folder (so nothing will be cut out) but it keeps going back to the default mask with cut corners.

I have also changed the file FieldMask.png to a plain white image, this one actually works, when a field spell is applied it takes into account my new mask.

why isn’t PlaymatMask.png working when modified ?