Diagnostic:
[[ 2.65333333e+04 0.00000000e+00 -1.32666667e+04 1.32666667e+04
0.00000000e+00 0.00000000e+00 0.00000000e+00 0.00000000e+00
0.00000000e+00]
[ 0.00000000e+00 7.85333333e+05 0.00000000e+00 0.00000000e+00
-3.92666667e+05 0.00000000e+00 0.00000000e+00 0.00000000e+00
0.00000000e+00]
[ -1.32666667e+04 0.00000000e+00 1.76888889e+04 -1.81898940e-12
0.00000000e+00 -8.84444444e+03 1.32666667e+04 0.00000000e+00
0.00000000e+00]
[ 1.32666667e+04 0.00000000e+00 -1.81898940e-12 5.30666667e+04
0.00000000e+00 -1.32666667e+04 1.32666667e+04 0.00000000e+00
0.00000000e+00]
[ 0.00000000e+00 -3.92666667e+05 0.00000000e+00 0.00000000e+00
5.89000000e+05 0.00000000e+00 0.00000000e+00 -1.96333333e+05
0.00000000e+00]
[ 0.00000000e+00 0.00000000e+00 -8.84444444e+03 -1.32666667e+04
0.00000000e+00 7.85333333e+25 -9.95000000e+03 0.00000000e+00
3.31666667e+03]
[ 0.00000000e+00 0.00000000e+00 1.32666667e+04 1.32666667e+04
0.00000000e+00 -9.95000000e+03 3.98000000e+04 0.00000000e+00
6.63333333e+03]
[ 0.00000000e+00 0.00000000e+00 0.00000000e+00 0.00000000e+00
-1.96333333e+05 0.00000000e+00 0.00000000e+00 1.96333333e+05
0.00000000e+00]
[ 0.00000000e+00 0.00000000e+00 0.00000000e+00 0.00000000e+00
0.00000000e+00 3.31666667e+03 6.63333333e+03 0.00000000e+00
1.32666667e+04]
Notice in the listing of stiffness that the term (6,6) is 7.85333333e+25, which is large, compared with other diagonal terms of the structure stiffness matrix. Evidently, the program uses 1e20 as a large multiplier and the large diagonal terms of the structure stiffness matrix before modification was 7.85333333e+05. The product of the large multiplier and the greatest diagonal term is the large number, 7.85333333e+25, used in the solution.
The next table lists the structure load matrix, Ps, and the structure displacement matrix, us. Notice that the 6-th row of the load matrix is the prescribed (specified) displacement, multiplied by the large number. That insures that after the solution the corresponding term of us is the specified displacement.