Mongoose not returning data when MongoDB shell returns

[Mark Voris]

I have been struggling where occasionally Mongoose doesn't return data even though if I manually run the query in MongoDB Compass and it works.  Here is my code

STUDIES.MODEL.JS

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

const studySchema = new Schema({
    region: String,
    studyID: String,
    locationName: String,
    date: Date,
    dayOfYear: Number,
    volunteer: String,
    inmateID: String,
    inmateName: String,
    notes: String
});

module.exports = mongoose.model('Studies', studySchema, 'studies');

const Study = require('../models/studies.model.js');

let filter = req.params.locationName;(being passed by Nodejs)
let visitDates = [];

let query = Study.find();
query.where({locationName: filter})
    .exec(function (err, studies)  {
            visitDates.push({
                date: studies.date,
                dayOfYear: studies.dayOfYear,
                volunteer: studies.volunteer,
                inmateNumber: studies.inmateNumber,
                inmateName: studies.inmateName
            })
    });

studies return with no data