[Ethereum] Error: nonce too low

This line:

var count = Web3.eth.getTransactionCount(defaultAccount,'pending');

You're starting your count at the number of outstanding/pending transactions the node is aware of. That's the wrong queue.

You could start here:

var count = Web3.eth.getTransactionCount(defaultAccount);

This will drop the next transaction on the nonce that follows the last known confirmed transaction.

It's not a good pattern, generally, to rely on the node's transaction count to set the nonce. Ideally, the software client will be aware of every transaction sent from the account and will know the correct number without asking.

Have a look over here for more info: Why does sendSignedTransaction return a tx hash BUT does not post to the Rinkeby network (React, Metamask, web3, infura)

And here: Concurrency patterns for account nonce

Hope it helps.

Run it again.

More generally, run it inside a try/catch block until success.

For your specific error, it is possible that the node is not synchronized with your account's current nonce, so you may want to add this to your options object:

nonce: await web3.eth.getTransactionCount(0xYourAccountAddress)

Since you may also encounter other types of errors, I suggest that you try this:

async function scan(message) {
    process.stdout.write(message);
    return await new Promise(function(resolve, reject) {
        process.stdin.resume();
        process.stdin.once("data", function(data) {
            process.stdin.pause();
            resolve(data.toString().trim());
        });
    });
}

async function getTransactionReceipt(web3) {
    while (true) {
        const hash = await scan("Enter transaction-hash or leave empty to retry: ");
        if (/^0x([0-9A-Fa-f]{64})$/.test(hash)) {
            const receipt = await web3.eth.getTransactionReceipt(hash);
            if (receipt)
                return receipt;
            console.log("Invalid transaction-hash");
        }
        else if (hash) {
            console.log("Illegal transaction-hash");
        }
        else {
            return null;
        }
    }
}

async function send(web3, account, data, gas) {
    while (true) {
        try {
            const options = {
                nonce: await web3.eth.getTransactionCount(account.address),
                data: "0x" + data,
                gas: gas
            };
            const signed = await web3.eth.accounts.signTransaction(options, account.privateKey);
            const receipt = await web3.eth.sendSignedTransaction(signed.rawTransaction);
            return receipt;
        }
        catch (error) {
            console.log(error.message);
            const receipt = await getTransactionReceipt(web3);
            if (receipt)
                return receipt;
        }
    }
}

async function finalDeploy(r) {
    const account = web3.eth.accounts.privateKeyToAccount(privateKey1);
    for (let i = 0; i < constructorParams.length; i++) {
        const receipt = await send(web3, account, myBin[r] + constructorParams[i], 5000000);
        console.log("Contract: " + r + " is deployed at " + receipt.contractAddress);
        contractAddressess.push(receipt.contractAddress)
    }
}