I've isolate the error to being in the following part, if I delete this section the bot functions without any errors:
function refund(sender, amount) {
steem.broadcast.transfer(config.private_active_key, config.account_name, sender, amount, '', function (err, response) {
if (err || !result) {
console.log("Refund failed ! For: " + sender);
}
}
});
}