ValueError: shape mismatch: objects can not be broadcast to a single shape because a variable is modified "alone"

I am a code and depending on what values I give to one of the variables, it works well or gives me the following error:

  

ValueError: shape mismatch: objects can not be broadcast to a single   shape

I've been going over everything. I have located the point where I get the error and I think the why. Which brings me to something a little strange.

The line where I get the error is in the second of these two:

leng_half_mask = np.int(leng_mask / 2)

vern = tls.vernier(mask, mask_star, leng_half_mask, leng_m_star_small)

mask and mask_star are lists and leng_half_mask and leng_m_star_small are scalars. When I run the entire program to the first line ( leng_half_mask ), the size of mask is 370 and that of mask_star is 368 . When I execute the next line ( vern ) these values are modified and have a size of 372 each. I think that by executing the line vern and entering the function, the fact that mask and mask_star have different sizes generates some conflict. But why is the size of mask and mask_star modified?

The tls.vernier function that I call has the following definition. For this function to do what it should, it is necessary that A and B be the same size. If they are of different sizes, then add zeros to the shortest list until both lists are of equal size.:

def vernier(A, B, cA, cB):

    long_A = len(A)
    long_B = len(B)

    dist_0cA = cA + 1
    dist_0cB = cB + 1

    dist_cAend = long_A - cA
    dist_cBend = long_B - cB

    dif_0 = dist_0cA - dist_0cB
    dif_end = dist_cAend - dist_cBend

    d0_abs = np.abs(dif_0)

    if dif_0 < 0:
        for i in range(0, d0_abs):
            A.insert(0, 0)
    elif dif_0 > 0:
        for j in range(0, d0_abs):
            B.insert(0, 0)

    de_abs = np.abs(dif_end)

    if dif_end < 0:
        for k in range(0, de_abs):
            A.append(0)
    elif dif_end > 0:
        for l in range(0, de_abs):
            B.append(0)

    long = len(A)
    vernier = []
    for m in range(0, long):
        if A[m] == 1 or B[m] == 1:
            vernier.append(1)
        else:
            vernier.append(0)

    return vernier