Multiple sorting in aggregate with mongo - mongodb

Question

When I use a multiple sorting in aggregate method with mongo, results aren't sorting in the right way. This is my query :
db.MyCollection.aggregate(
{
"$unwind": "$objects"
},
{
"$lookup": {
"from": "CollectionA",
"localField": "objects.itemId",
"foreignField": "_id",
"as": "itemOne"
}
},
{
"$lookup": {
"from": "CollectionB",
"localField": "user_id",
"foreignField": "id",
"as": "users"
}
},
{
"$lookup": {
"from": "CollectionC",
"localField": "objects.itemName",
"foreignField": "name",
"as": "itemTwo"
}
},
{
"$addFields": {
"item": {
"$arrayElemAt": [
"$itemOne",
0
]
},
"user": {
"$arrayElemAt": [
"$users",
0
]
},
"itemP": {
"$arrayElemAt": [
"$itemTwo",
0
]
}
}
},
{
"$addFields": {
"itemName": {
"$ifNull": [
"$item.name",
"$objects.itemName"
]
},
"userName": {
"$concat": [
"$user.firstname",
" ",
"$user.lastname"
]
}
}
},
{
"$match": {
"client_id": 2
}
},
{
"$skip": 1
},
{
"$limit": 10
},
{
"$project": {
"date": "$objects.date",
"state": "$objects.state"
}
},
{
"$sort": {
"objects.state": 1,
"objects.date": 1,
}
}
)
To precise: "date" field is Date type and "state" field is number type.
If I use only one sort : result order is correct. But if I use 2 sorts, results are not order correctly. Have you got any ideas, why ?

Answer 1

As #Neil Lunn says :
They don't sort correctly because you renamed the fields in $project. So it should be { $sort: { state: 1, date: 1 } }