Error deploying contract via Truffle to Polygon mainnet

Question

When I try deploying with command npx truffle migrate --config=truffle-config.js --network polygon, I get the following error.

Error [ERR_UNHANDLED_ERROR]: Unhandled error. ([object Object])
    at Web3ProviderEngine.emit (events.js:177:17)
    at self._getBlockByNumberWithRetry (/Users/me/contracts/node_modules/@trufflesuite/web3-provider-engine/index.js:57:14)
    at afterRequest (/Users/me/contracts/node_modules/@trufflesuite/web3-provider-engine/index.js:151:21)
    at _handleAsync (/Users/me/contracts/node_modules/@trufflesuite/web3-provider-engine/index.js:176:21)
    at /Users/me/contracts/node_modules/@trufflesuite/web3-provider-engine/index.js:238:9
    at /Users/me/contracts/node_modules/async/internal/once.js:12:16
    at replenish (/Users/me/contracts/node_modules/async/internal/eachOfLimit.js:61:25)
    at /Users/me/contracts/node_modules/async/internal/eachOfLimit.js:71:9
    at eachLimit (/Users/me/contracts/node_modules/async/eachLimit.js:43:36)
    at /Users/me/contracts/node_modules/async/internal/doLimit.js:9:16
    at end (/Users/me/contracts/node_modules/@trufflesuite/web3-provider-engine/index.js:217:5)
    at Request._callback (/Users/me/contracts/node_modules/@trufflesuite/web3-provider-engine/subproviders/rpc.js:36:21)
    at self.callback (/Users/me/contracts/node_modules/request/request.js:185:22)
    at Request.emit (events.js:188:13)
    at ClientRequest.<anonymous> (/Users/me/contracts/node_modules/request/request.js:819:16)
    at Object.onceWrapper (events.js:276:13)
    at ClientRequest.emit (events.js:188:13)
    at TLSSocket.emitRequestTimeout (_http_client.js:668:40)
    at Object.onceWrapper (events.js:276:13)
    at TLSSocket.emit (events.js:188:13)
    at TLSSocket.Socket._onTimeout (net.js:446:8)
    at listOnTimeout (timers.js:324:15)
    at processTimers (timers.js:268:5)

It seems like it's some kind of timeout error, perhaps infura node related? I also posted my ./truffle-config.js and ./migration/2_deploy_all.js script below.

truffle migrations script (./migrations/2_deploy_all.js):

var RedeemableERC20 = artifacts.require('RedeemableERC20');

module.exports = function(deployer) {
    deployer.deploy(RedeemableERC20);
};

my ./truffle-config.js file:

var NonceTrackerSubprovider = require('web3-provider-engine/subproviders/nonce-tracker');
var HDWalletProvider = require('@truffle/hdwallet-provider');

var mnemonic = process.env.CONTRACTS_MNEMONIC_SEED;
var node_url = process.env.ETH_NODE_URL;
var infura_key = process.env.INFURA_KEY;

if (!mnemonic || !node_url) {
    console.log(
        'WARN: mnemonic or eth_node env variables not set, see README.md'
    );
}

module.exports = {
    contracts_build_directory: './build/contracts',
    contracts_directory: './contracts',
    compilers: {
        solc: {
            version: '^0.8.3',
            settings: {
                optimizer: {
                    enabled: true,
                    runs: 200,
                },
            },
        },
    },
    networks: {
        ganache: {
            host: 'localhost',
            port: 7545,
            network_id: '5777',
            gas: 4000000,
            gasPrice: 1000000000,
        },
        rinkeby: {
            provider: function() {
                return new HDWalletProvider(mnemonic, node_url);
            },
            network_id: '4', // Rinkeby ID 4
            gas: 4000000,
            gasPrice: 1000000000,
        },
        polygon: {
            provider: () =>
                new HDWalletProvider(
                    mnemonic,
                    'https://polygon-mainnet.infura.io/v3/' + infura_key
                ),
            network_id: 137,
            confirmations: 2,
            timeoutBlocks: 200,
            skipDryRun: true,
            chainId: 137,
            gas: 6600000,
            gasPrice: 600000000000,
        },
        mainnet: {
            provider: () => new HDWalletProvider(mnemonic, node_url),
            network_id: 1,
            confirmations: 2,
            gas: 660000, // 21,000 normal; 1,685,639 used by v1 Flower Contract
            gasPrice: 140000000000, // 140 gwei
        },
    },
};

/* vim: set ts=2 sw=2: */

Has anyone experienced this before?