Estimar gas para contrato inteligente siempre falla

Implementé un contrato muy simple en la cadena de bloques de Ethereum para poder dividir un pago en dos salidas diferentes.

pragma solidity ^0.5.0;

contract MoonTrade
{
    function multiSendETH(  address payable address1,
                            uint value1,
                            address payable address2,
                            uint value2) public payable
    {
        address1.transfer(value1);
        address2.transfer(value2);

        msg.sender.transfer(address(this).balance);
    }
}

Está en la red de prueba de Ropsten. https://ropsten.etherscan.io/address/0x3376a6d3e46496944fe7afd838efb949007b80f4

estoy usando web3py (python)

Sin embargo, cada vez que intento hacerlo web3.eth.estimateGas(), siempre aparece un error que dice:

El gas requerido excede la asignación o la transacción siempre falla (código de error -32000)

No estoy seguro de lo que estoy haciendo mal aquí.

Aquí está la entrada que estoy pasando para estimar el gas:

{'to': 0x3376a6D3e46496944fe7afD838EfB949007B80f4, 
    'from': 0xF811E7eD1BBc908f33b1C298087220D249bE0464, 
    'value': 50000000000000000, 
    'data': b'{"name": "multiSendETH", "types": ["address","uint256","address","uint256"],"inputs":["0xbe623C1f9F47d2105f80A9A5c0Cd90562be5fA58", "40000000000000000","0x366de12a1A6fd0B140153f011c1A085314A047BC", "10000000000000000"]}'}

La parte de datos obviamente se convierte en bytes web3.toBytes()antes de pasar a la función de estimación de gas.

No tengo ni idea de si este error está relacionado con mi contrato inteligente o con la forma en que estoy pasando los parámetros al gas estimado.

¿Algunas ideas?

Aquí está mi salida de depuración:

ABI: [{"constant": false,"inputs": [{"name": "address1","type": "address"},{"name": "value1","type": "uint256"},{"name": "address2","type": "address"},{"name": "value2","type": "uint256"}],"name": "multiSendETH","outputs": [],"payable": true,"stateMutability": "payable","type": "function"}]

Contract address: 0x60946D10048EC9fbB0A260bb17da2eFEbdb76F12

Estimate gas data: {'to': 0x60946D10048EC9fbB0A260bb17da2eFEbdb76F12, 'from': 0xF811E7eD1BBc908f33b1C298087220D249bE0464, 'value': 50000000000000000, 'data': b'{"name": "multiSendETH", "types": ["address","uint256","address","uint256"],"inputs":["0xbe623C1f9F47d2105f80A9A5c0Cd90562be5fA58", "40000000000000000","0x366de12a1A6fd0B140153f011c1A085314A047BC", "10000000000000000"]}'}

Total gas fee in WEI: 6600000000000000

Gas price in WEI: 22000000000

Transaction data to be used: {"name": "multiSendETH", "types": ["address","uint256","address","uint256"],"inputs":["0xbe623C1f9F47d2105f80A9A5c0Cd90562be5fA58", "33400000000000000","0x366de12a1A6fd0B140153f011c1A085314A047BC", "10000000000000000"]}

Signed transaction: AttrDict({'rawTransaction': HexBytes('0xf901488085051f4d5c00830493e09460946d10048ec9fbb0a260bb17da2efebdb76f1287b1a2bc2ec50000b8db7b226e616d65223a20226d756c746953656e64455448222c20227479706573223a205b2261646472657373222c2275696e74323536222c2261646472657373222c2275696e74323536225d2c22696e70757473223a5b22307862653632334331663946343764323130356638304139413563304364393035363262653566413538222c20223333343030303030303030303030303030222c22307833363664653132613141366664304231343031353366303131633141303835333134413034374243222c20223130303030303030303030303030303030225d7d1ba0ba8a017590df650113bbe37c75271013750180e3464145b174baa39318d4d5c4a076c352add8de85ae019ee52949afb54d2a30105e1abe0cc70cd6fef351dbff4c'), 'hash': HexBytes('0x6f4e47b48d1c4e37fc360d97f5e15a05e6100a6058b33442419617c536690e33'), 'r': 84374024802743941308955771074764079224633082170439044639020403769288422643140, 's': 53718021940567424333967254769074396806767762625919492526766162521994190126924, 'v': 27})

Gas: 3E-13

Gas price: 2.2E-8

Value: 0.05

Gas * gasprice + value = 0.0566

{"error":"{'code': -32000, 'message': 'insufficient funds for gas * price + value'}"}