Why is it that sometimes the data range acquired exceeds the range?

There is a limit to the measurement range of the BMM350, i.e. the sum of the absolute values for each axis should be less than this value. That is, SQRT(Hx^2 + Hy^2 + Hz^2) = 2000uT

You can refer to chapter 5.3 of the BMM350 datasheet below.