Hello Dennis,
When you draw a Grid, always you need intervals of values X and Z, are repeated if you want the points of Grid are drawn correctly, therefore, you can not add diferents values X or Z in the diferent intervals. For example, in your code you have added next values X:
First interval X: 0,10,25.
Second interval X : 0,11,25(Wrong)
Third interval X:0,12,25.(Wrong)
If you want to Grid is drawn correctly, you need add the same interval values X,so,correct way is:
First interval X: 0,10,25.
Second interval X : 0,10,25(Correct)
Third interval X:0,10,25.(Correct)
In your case the Interval of Z valuesm is correct.
I recommend you take a look in this
thread to see the correct way to add values in Grid.
I hope will helps.
Thanks,