nodejs mongodb timesSeries sometimes hangs without errors - node.js

Question

Im running a script that has multiple queries using timesSeries loop.
sometimes it hangs for no reason or errors. first it usese count, to
determine how many loops for the pages. then it loops to lessen results.
then it async loops to build the document to send to google bigquery.
sometimes it just stops, then I have to kill script manually. should I close the count first also?
mongo_client.connect(mongo_url, function(err, db) {
var query = { "date_visited" : {$gt: new Date("2016-01-01T00:00:00.000Z"),$lt: new Date("2016-02-01T00:00:00.000Z")},_id:{$gte: ObjectId("56aabfe8c6edfd0d608b480e")} };
db.collection(collection_name).count(query,function(err, count){
var pages = Math.ceil(count/limit);
//var pages = 1;
console.log("count: "+count);
console.log("pages: "+pages);
var page = 0
async.timesSeries(pages, function(page, next)
{
var skip = page * limit;
var current_page = page+1;
console.log("skip: "+skip);
console.log("page: "+page);
console.log("current_page: "+current_page+" of "+pages);
var documents = [];
var x=1;
db.collection(collection_name).find(query).limit(limit).skip(skip).toArray(function(err, db_results) {
async.each(db_results, function (db_resultsx, cb) {
var account_id = db_resultsx.account_id;
delete db_resultsx.upsell_detect;
db_resultsx._id = db_resultsx._id.toString();
db_resultsx.xdate_visited = moment(db_resultsx.date_visited).format("YYYY-MM-DD hh:mm:ss");
documents.push(db_resultsx);
//console.log(documents);
if(documents.length == db_results.length) {
bigqueryClient
.dataset(dataset)
.table(collection_name)
.insert(documents)
.then((insertErrors) => {
console.log("Inserted: "+page);
//console.error("Inserted: "+page);
//console.error(insertErrors);
next();
if (insertErrors && insertErrors.length > 0) {
console.log("start errors: "+page+"("+insertErrors.length+")");
insertErrors.forEach((err) => console.log(JSON.stringify(err, null, 4)));
console.log("done errors: "+page);
console.log("done on: "+moment().format("YYYY-MM-DD hh:mm:ss"));
}
})
.catch((err) => {
console.log('ERROR:');
console.log(JSON.stringify(err, null, 4));
console.log('done catch:'+page);
process.exit();
});
}
});
});
},
function(err, coll)
{
console.log("done all");
console.log(query);
setTimeout(function () {
db.close();
console.error("DONE");
process.exit();
}, 60000);
});
});
});