I'd call that a gouge rather than a scratch. To use that unit, I'd definitely sand/file/grind it out so that it has a gradual taper to the main part of the unit. Take a piece of wood about the same size and try breaking it. Now put a deep gouge/scratch like that in the same area of the piece of wood and try breaking it. You'll most likely be able to break that piece of wood fairily easily and the break will happen on or close to where the gouge/scratch is. that's why it's called a stress riser; it concentrates stresses to that locale.

Cheers