MATLAB: Different results in symbol integration

Dear all,

whats going wrong here? I only changed the order of the dependend variables from (x1,x2,x3,x4) to (x2,x1,x3,x4).

syms x1 x2 x3 x4

Variant 1:

f(x1,x2,x3,x4)=exp(-x1^2)*exp(-x2^2)*exp(-x3^2)*exp(-x4^2)*x1;
F(x1,x2,x3,x4)=int(int(int(int(int(f,x1),x2),x3),x4));

Result: F(1,1,1,1)

= -(pi^2*erf(x1)*erf(x2)*erf(x3)*erf(x4))/32
= -0.1555

Variant 2:

f(x2,x1,x3,x4)=exp(-x1^2)*exp(-x2^2)*exp(-x3^2)*exp(-x4^2)*x1
F(x2,x1,x3,x4)=int(int(int(int(int(f,x1),x2),x3),x4));

Result: F(1,1,1,1)

= -(pi^(3/2)*exp(-x1^2)*erf(x3)*erf(x4)*(exp(-x2^2)/pi^(1/2) + x2*erf(x2)))/16
= -0.0955

Regards

System:

Linux Ubuntu 18.04

MATLAB R2018a