async.waterfall randomly sorts results - node.js

Question

I was writing a nest code, tried using async.waterfall or async.series but I am getting random results every time I refresh. it seems to be because of the queries of the first 2 functions randomly finishing.
first query was sorting to committed_date DESC. but when I add the 2 sub queries. the sort gets distorted.
Step1: Loop landingpages
Step1.1 - fetch details1 repositories
Step1.2 - fetch details2 versions
Step2: build array
db.collection('landingpages').find({is_deleted:{$ne:1}}).sort({committed_date:-1}).limit(10).toArray(function(err, db_results) {
var data_array = [];
var x=1;
if(db_results.length == 0) {
return_data.lps = data_array;
parallel_done();
}else{
async.each(db_results, function (db_results1, cb) {
async.watefall(
[
function(callback) {
//if this is removed or passed as callback(null, ""); the sort is fixed from committed - 1
var data_repo = {};
db.collection('repositories').find({repository_id: repository_id}).toArray(function(err, db_results1) {
if(db_results1.length == 0){
var data_repo = {};
callback(null, data_repo);
}else{
var data_repo = db_results1[0];
callback(null, data_repo);
}
});
},
function(callback) {
//if this is removed or passed as callback(null, ""); the sort is fixed from committed - 1
var data_version = {};
db.collection('versions').find({landingpage_id: landingpage_id}).sort({_id:-1}).limit(1).toArray(function(err, db_results1) {
if(db_results1.length == 0){
var data_version = {};
callback(null, data_version);
}else{
var data_version = db_results1[0];
callback(null, data_version);
}
});
}
],
function (err, data_repo,data_version) {
var document = {
"x": x++,
"landingpage_id": db_results1.landingpage_id,
"repository_id": db_results1.repository_id,
"version_id": data_version.version_id,
"val": db_results1,
"data_repo": data_repo,
"data_version": data_version,
};
data_array.push(document);
if(data_array.length == db_results.length) {
return_data.lps = data_array;
}
}
);
});
}
});