AES-GCM decryption error iaik.cms.CMSException: Unable to decrypt encrypted content-encryption key: Invalid padding - aes-gcm

Question

I am using following code to encrypt data using AES-GCM:
// the stream to which to write the EnvelopedData
ByteArrayOutputStream resultStream = new ByteArrayOutputStream();
EnvelopedDataOutputStream envelopedData;
// wrap EnvelopedData into a ContentInfo
ContentInfoOutputStream contentInfoStream =
new ContentInfoOutputStream(ObjectID.cms_envelopedData, resultStream);
// create a new EnvelopedData object encrypted with AES
try {
envelopedData = new EnvelopedDataOutputStream(contentInfoStream,
(AlgorithmID)AlgorithmID.aes256_GCM.clone());
} catch (NoSuchAlgorithmException ex) {
throw new CMSException("No implementation for AES.");
}
// create the recipient infos
RecipientInfo[] recipients = new RecipientInfo[1];
// user1 is the first receiver
recipients[0] = new KeyTransRecipientInfo(signCert,
(AlgorithmID)AlgorithmID.rsaEncryption.clone());
// specify the recipients of the encrypted message
envelopedData.setRecipientInfos(recipients);
//int blockSize = 2048; // in real world we would use a block size like 2048
// write in the data to be encrypted
//byte[] buffer = new byte[blockSize];
byte[] buffer = new byte[16];
//byte[] buffer;
int bytesRead;
while ((bytesRead = inputstream.read(buffer)) != -1) {
envelopedData.write(buffer, 0, bytesRead);
}
But while trying to decrypt the same using following code:
EnvelopedDataStream enveloped_data = new EnvelopedDataStream(is);
enveloped_data.setupCipher(privateSignKey, 0);
InputStream decrypted = enveloped_data.getInputStream();
ByteArrayOutputStream os = new ByteArrayOutputStream();
ByteStreams.copy(decrypted, os);
os.close();
I am getting following error:
iaik.cms.CMSException: Unable to decrypt encrypted content-encryption key: Invalid padding!
I am not sure of block size to be used, this might be a reason for the error, but not sure.
Moreover, if I compare my encrypted file with that of a correct one, I see following difference:
My encrypted data:
OBJECT IDENTIFIER 2.16.840.1.101.3.4.1.46 aes256-GCM (NIST Algorithm)
SEQUENCE (1 elem)
OCTET STRING (12 byte) FE5729470184A04A5AA30158
Correct data:
OBJECT IDENTIFIER 2.16.840.1.101.3.4.1.46 aes256-GCM (NIST Algorithm)
SEQUENCE (2 elem)
OCTET STRING (12 byte) CA985F7EAFB709DF711DCA2A
INTEGER 16
Could you please help us in getting this to work?