There's an error with decryption of the message encrypeted through AES-256 after sending

Question

I use AES-256 refer Encrypt & Decrypt using PyCrypto AES 256. However there is a some error while decoding.

  File "/home/client.py", line 60, in receive
    print('%s :' %opp_id, aes.decrypt(recvData))
  File "/home/client.py", line 31, in decrypt
    return self._unpad(cipher.decrypt(enc[AES.block_size:])).decode('utf-8')
  File "/home/PycharmProjects/qkd-chat/venv/lib/python3.9/site-packages/Crypto/Cipher/blockalgo.py", line 295, in decrypt
    return self._cipher.decrypt(ciphertext)


ValueError: Input strings must be a multiple of 16 in length

The code below is part for AES-256.

class AESCipher(object):
    def __init__(self, key):
        self.bs = AES.block_size
        self.key = hashlib.sha256(key.encode()).digest()

    def encrypt(self, raw):
        raw = self._pad(raw)
        iv = Random.new().read(AES.block_size)
        cipher = AES.new(self.key, AES.MODE_CBC, iv)
        return base64.b64encode(iv + cipher.encrypt(raw.encode()))

    def decrypt(self, enc):
        enc = base64.b64decode(enc)
        iv = enc[:AES.block_size]
        cipher = AES.new(self.key, AES.MODE_CBC, iv)
        return self._unpad(cipher.decrypt(enc[AES.block_size:])).decode('utf-8')

    def _pad(self, s):
        return s + (self.bs - len(s) % self.bs) * chr(self.bs - len(s) % self.bs)

    @staticmethod
    def _unpad(s):
        return s[:-ord(s[len(s)-1:])]

this is the part of socket programming

def send(sock):
    while True:
        try:
            aes = AESCipher(key)
            sendData = aes.encrypt(input())
            # sendData = encrypt(key, input())
            sock.send(sendData)
        except:
            continue

def receive(sock):
    while True:
        recvData = sock.recv(4096)
        try:
            aes = AESCipher(key)
            print('%s :' %opp_id, aes.decrypt(recvData))
        except DecryptionException as e:
            print(e)

I think there is an error in receive message because there is a some change in error message when I change the number in sock.recv( - )