XTEA-based encryption to handle up to 128bit block size

Question

As learning to be an electronic engineer, my lecturer has requested, based on the original Xtea, to develop the FPGA solution to run 128-bit block size and 128-bit key size cryptography. I have decided to solve it by dividing the 128-bit block into four 32-bit blocks and running as double encryption. I wanted to make sure mathematics was correct first. There is the Python code I have developed. However, the decription process is not correct. Could anyone help me with that?

Python code:

def xtea_encipher_128_modified(num_rounds, v, k):
    y, z, w, x = v
    DELTA = 0x9e3779b9  # (sqrt(5) - 1) * 2**31
    sum = 0
    for _ in range(num_rounds):
        y += ((z << 4) ^ (z >> 5)) + z ^ (sum + k[sum & 3])
        y = y & 0xffffffff  # Ensure y stays within 32-bit bounds
        sum = (sum + DELTA) & 0xffffffff
        z += ((y << 4) ^ (y >> 5)) + y ^ (sum + k[sum >> 11 & 3])
        z = z & 0xffffffff  # Ensure z stays within 32-bit bounds
    w += ((x &lt;&lt; 4) ^ (x &gt;&gt; 5)) + x ^ (sum + k[sum &amp; 3])
    w = w &amp; 0xffffffff  # Ensure w stays within 32-bit bounds
    sum = (sum + DELTA) &amp; 0xffffffff
    x += ((w &lt;&lt; 4) ^ (w &gt;&gt; 5)) + w ^ (sum + k[sum &gt;&gt; 11 &amp; 3])
    x = x &amp; 0xffffffff  # Ensure x stays within 32-bit bounds

return y, z, w, x


def xtea_decipher_128_modified(num_rounds, v, k):
    y, z, w, x = v
    DELTA = 0x9e3779b9  # (sqrt(5) - 1) * 2*31
    sum = (DELTA  num_rounds) & 0xffffffff
    for _ in range(num_rounds):
        x -= ((w << 4 ^ w >> 5) + w) ^ (sum + k[(sum >> 11) & 3])
        x = x & 0xffffffff  # Ensure x stays within 32-bit bounds
        sum = (sum - DELTA) & 0xffffffff
        w -= ((x << 4 ^ x >> 5) + x) ^ (sum + k[sum & 3])
        w = w & 0xffffffff  # Ensure w stays within 32-bit bounds
    z -= ((y &lt;&lt; 4 ^ y &gt;&gt; 5) + y) ^ (sum + k[(sum &gt;&gt; 11) &amp; 3])
    z = z &amp; 0xffffffff  # Ensure z stays within 32-bit bounds
    sum = (sum - DELTA) &amp; 0xffffffff
    y -= ((z &lt;&lt; 4 ^ z &gt;&gt; 5) + z) ^ (sum + k[sum &amp; 3])
    y = y &amp; 0xffffffff  # Ensure y stays within 32-bit bounds

return y, z, w, x


usage example
plaintext = (0xA5A5A5A5,0x01234567,0xFEDCBA98,0x5A5A5A5A)
key = (0xDEADBEEF,0x01234567,0x89ABCDEF, 0xDEADBEEF)
num_rounds = 32  # number of rounds
ciphertext = xtea_encipher_128_modified(num_rounds, plaintext, key)
print(ciphertext)
plaintext = xtea_decipher_128_modified(num_rounds, ciphertext, key)
print(plaintext)