nsimplify, make zero the really small numbers in the matrix

[quest]

Ok, I found the reason :)))

The thing is that my real matrix is coming from another mathematical process. And when I print my real matrix, I used this line:

np.set_printoptions(precision=3) #"rounding"

so real matrix came as normal
However I should have used this code line

realmat=realmat.round(3)

Because with the previous script, I was printing in a normal shape but I wasn't actually changing the my real matrix. so when I multiply my real matrix and the symbolic matrix, I had this issue

Now it is ok :)
Thanks