Why does mongoose hang when creating an element?

Question

MongoDB

console.log('searching');

let user = await UserModel.findOne(params);
console.log('search finished');

if (user == null) {
    console.log('nothing');
    user = await new UserModel(params).save(); // <== на этой строке зависает
    console.log('created');
}

return user;

Why can it hang when trying to create an element? Search is made normally and sessions work. Doesn't write any errors. The table itself is created (if fields with indexes are used). To be honest, I don't quite understand how to debug this.
If you make a request directly in the same place, then everything will work correctly:

const data = await db().collection("users").insertOne(params);

Answer 1

I found the reason - it turns out I was stupid.
I had a pre-save method in the schema and forgot to call next on it.