SOLVED: scipy.optimize.least_squares problem

[Gribouillis]

The error message is clear. The 'least_squares' function expects 'system1' to return a 1-d array_like. Looking in the documentation, it is said that

The argument x passed to this function is an ndarray of shape (n,) (never a scalar, even for n=1). It must allocate and return a 1-D array_like of shape (m,) or a scalar.

I suggest that you check the shape of the value returned by system1() and raise an exception if it is not a tuple with one element like (m,) to understand the problem.