ValueError: setting an array element with a sequence when array is not a sequence

Hello this code is intended to store the coordinates of rectangles drawn with open cv and compile the results into a single image.

import numpy as np
import cv2

im = cv2.imread('1.jpg')
im3 = im.copy()

gray = cv2.cvtColor(im,cv2.COLOR_BGR2GRAY)
blur = cv2.GaussianBlur(gray,(5,5),0)
thresh = cv2.adaptiveThreshold(blur,255,1,1,11,2)



contours,hierarchy = cv2.findContours(thresh,cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)


squares = []

for cnt in contours:
    if cv2.contourArea(cnt)>50:
        [x,y,w,h] = cv2.boundingRect(cnt)

        if  h>28 and h<34:
            rect = (cv2.rectangle(im,(x,y),(x+w,y+h),(255,255,255),3))
            squares.append(cv2.boundingRect(cnt))
            cv2.imwrite('norm1.jpg',im)

crop_img = [[255 for x in xrange(377)] for x in xrange(377) ]

for s in squares:
    s = squares[0]
    x = s[0]
    y = s[1]
    w = s[2]
    h = s[3]
    img = im[y:y+h,x:x+w]
    for col in range(y,y+h):
        for row in range(x,x+w):
            if img[col - y][row - x].tolist() == [0,0,0]:
                crop_img[col][row] = [0,0,0]



cv2.imwrite("cropped.jpg", np.array(crop_img))

However, it throws this error message

File "C:\Users\Program\Desktop\new  1.py", line 43, in <module>
    cv2.imwrite("cropped.jpg", np.array(crop_img))
ValueError: setting an array element with a sequence

I have read that this can be caused by an "uneven" matrix but after several rounds of testing I have confirmed that it is indeed a square 377 x 377 matrix

For reference: "1.jpg" is the image shown below

Any leads as to how to fix this error would be greatly appreciated!