MongoDB How to get rid of duplicates in response - mongodb

Question

I need to get user chats by user id. The response adds the last message to select as follows: get one last message for each chat whose creation time $last_message.create_date is greater than or equal to chatsusers.start_message_id.
db.chat.aggregate([
{
$match: {
participants: "63ce54460aeee5e72c778d90"
}
},
{
$lookup: {
from: "chatsusers",
localField: "id",
foreignField: "chat_id",
as: "chat_user"
}
},
{
$unwind: {
path: "$chat_user"
}
},
{
$lookup: {
from: "message",
localField: "id",
foreignField: "chat_id",
let: {
smid: "$chat_user.start_message_id"
},
pipeline: [
{
$match: {
$expr: {
$gte: [
"$create_date",
"$$smid"
]
}
}
},
{
$sort: {
create_date: -1
}
},
{
$limit: 1
}
],
as: "last_message",
}
},
{
$unwind: {
path: "$last_message",
preserveNullAndEmptyArrays: true
}
},
{
$project: {
id: 1,
title: 1,
create_date: 1,
type: 1,
participants: 1,
owner_id: 1,
last_message: "$last_message",
unread: 1
}
}
])
Problem: You can see in the examples below:
First: duplicate messages in the response to my query, the first object is identical to the second First example
Second: the first object in the response is correct, but the second is a duplicate that for some reason didn't work sample and it has (though it shouldn't have) the last message that $last_message.create_date must be greater than or equal to chatsusers.start_message_id Second example
How do I get rid of the duplication in the response to my request?