raw transactions to send ERC20 token fails on private network(POA)

Question

I am trying to transfer ERC20 tokens on private ethereum network(POA)

Transaction flow:

1. raw tx object creation on backend.

   {
        "gasLimit": 37000,
        "gasPrice": 4000000000,
        "to": <contract address>,
        "value": 0,
        "chainId": 15,
        "data": "0xa9059cbb000000000000000000000000ff70ccdc55a319428fd88809ce848a61087ab2ac0000000000000000000000000000000000000000000000003782dace9d900000"
    }

2. sign tx on front end.

 { messageHash:
   '0x4bbc38ad53cf154ca1445365c9007dfeca0c0cce251945feb2a8ff3bd6de8795',
  v: '0x42',
  r:
   '0xa664add8c614f05d52104a29b16312744cb8849bc5af5cb78a9ba7daf19e8a12',
  s:
   '0x38c055e9a7c1e5b0321f5d82d832d91da3a2207025756b84c44b8ca31cbbb4f2',
  rawTransaction:
   '0xf8a80884ee6b280082908894324e19e928239d0c7f8b93247d559b54a4e0d03080b844a9059cbb0000000000000000000000008d75f6db12c444e290db995f2650a68159364e2500000000000000000000000000000000000000000000000270801d946c94000042a0a664add8c614f05d52104a29b16312744cb8849bc5af5cb78a9ba7daf19e8a12a038c055e9a7c1e5b0321f5d82d832d91da3a2207025756b84c44b8ca31cbbb4f2' }

3. submit tx from backend data.

 web3.eth.sendSignedTransaction(signedData)
        .on('receipt',function(receipt:any){
            if(receipt.status == false)
                throw new Error('transaction failed');
            sendSuccessResponse(res, {
                txId : receipt.transactionHash
            });
        })
        .catch(function(error:any){
            next(error);
        })

But when I try to sign transaction on android(using web3j) and submit from backend(web3.js). It fails sometimes(for random receiving addresses such as : 0xFF70ccDC55a319428FD88809cE848a61087Ab2aC) with error: Transaction has been reverted by the EVM

    public String sign(RawTransaction rawTransaction, Credentials credentials) {
        byte[] signedMessage;
        signedMessage = TransactionEncoder.signMessage(rawTransaction, bigIntToByteArray(15), credentials);
        return Numeric.toHexString(signedMessage);
    }

version:

Web3.js - 1.2.4

Web3j - org.web3j:core:4.2.0-android

Geth - Geth/v1.9.6-stable-bd059680/linux-amd64/go1.11.5

Network consensus : POA

No. of nodes : 2

Answer 1

Transaction was failing because of fixed gasLimit : 37000.

Gas depends on what the function is doing.

For example, it is more expensive to set a zero-value storage value to non-zero, than it is to set a non-zero storage value to another non-zero storage value.

In my case it was because of SSTORE opcode as it takes 20000 when storage value is set to non-zero from zero and 5000 when the storage value's remains unchanged or is set to zero.

So changed 37000 to 52000 and it worked as expected.