4D, cubic spline lookup table is returing incorrect interpolated values

Hello,

I try to use a 4-Dimensional lookup table in Simulink, but it appears to return (in my opinion) incorrect values if I compare it with the interpn() method in Matlab. The lookup table uses cubic spline interpolation, and clipping as extrapolation method (although it does not get out of bounds). See the two figures as comparison:

Is there a fundamental difference between the two methods I do not know of?

Thank you for your help!