codeigniter 3.1.6 decrypt fails sometimes to get the correct value

I am using codeigniter 3.1.6. I am using encryption class and I loaded it through config/autoload.

PHP Code:

$autoload['libraries'] = array('database', 'session', 'xmlrpc','form_validation','encryption'); 


I have set the encryption key from 

PHP Code:

echo bin2hex($this->encryption->create_key(16)); 


PHP Code:

$config['encryption_key'] = hex2bin('ccf8ce9386eb83d67a3a334748aca064'); 


I am encrypting and decrypting using 

PHP Code:

$this->encryption->encrypt($data);
$this->encryption->decrypt($encrypteddata); 


The problem is that for 2 instances I succeed and the next one the form crash as you will see on the image attached.

Assistance is highly needed.

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