Hi!

I gave your code another look and I have a few suggestions
Change :
vec_set(grindblock.x, nullvector);
grindblock.x = 1;
to
vec_set(grindblock, vector(1,0,0));

and
vec_set(grindtrace, nullvector);
grindtrace.z = -1;
to
vec_set (grindtrace, vector(0,0,-1));

and
vec_set(grindheight, nullvector);
grindheight.z = -1;
to
vec_set(grindheight, vector(0,0,-1));


//-------------------
What vector are you changing?

vec_normalize(grindtrace, 100);
vec_normalize(grindheight, -47);
//----------------------