Populate within object only work in some function - node.js

Question

I'm having trouble dealing with populate within object, so I have a SosmedPost schema. I want to populate the Comments field, which is an array. Likewise, I have 2 function create comment and getPost, the populate working in create comment but in getPost it's not working
const SosmedPostSchema = new mongoose.Schema({
Username : {
type : String
},
Content : {
type : String
},
Documents : {
type : String
},
Author : {
type : mongoose.Schema.Types.ObjectId,
ref : 'sosmedprofiles'
},
Comments : [{
PostedBy : {
type : mongoose.Schema.Types.ObjectId,
ref : "sosmedprofiles"
},
Text : {
type : String
}
}],
Likes : [{
type : mongoose.Schema.Types.ObjectId,
ref : "sosmedprofiles"
}]
}, {timestamps : true});
I have a function to create comment, and it's working perfectly fine
const createComment = (req, res) => {
const Id = req.params.id;
const comment = {
Text : req.body.Text,
PostedBy : req.body.PostedBy
}
SosmedPostModel.findByIdAndUpdate({_id : Id}, {
$push : {Comments : comment}
}, {
new : true
}).populate("Comments.PostedBy")
.exec((err, result) => {
if (err) {
return res.status(422).json({error : err})
} else {
res.json(result)
}
})
}
But in another function getPostById the Comments.PostedBy populate its not working. Is there something wrong with how I populate the array ?
const getPostById = (req, res) => {
const Id = req.params.id;
SosmedPostModel.findById({_id : Id})
.populate("Author")
.populate("Comments.PostedBy")
.populate("Likes")
.exec(function (err, posts) {
if (err) return handleError(err);
res.send(posts)
})
}
This is the result in create comment function :
"Comments": [
{
"Text": "Cool Post",
"PostedBy": {
"_id": "63a116dc3c759e4437fabacb",
"Username": "rahmandhika5#gmail.com",
"FullName": "Rahmandhika",
"ProfilePicture": "https://example.jpg",
"Bio": "Live in Tangerang",
"Post": [],
"createdAt": "2022-12-20T01:58:52.179Z",
"updatedAt": "2022-12-20T01:58:52.179Z",
"__v": 0
},
"_id": "63a1172f3c759e4437fabaf9"
},
But in getPostById function, the result is :
"Comments": [
{
"Text": "Cool Post",
"PostedBy": "63a116dc3c759e4437fabacb",
"_id": "63a1172f3c759e4437fabaf9"
},
{
"Text": "Yo",
"PostedBy": "63a116dc3c759e4437fabacb",
"_id": "63a11bab4aad531ee8ad8273"
},
{
"PostedBy": "63a116dc3c759e4437fabacb",
"Text": "YAAY",
"_id": "63a11fcdf5384ab89174ad7e"
}
],