Window in PyQt5 has size restrictions from last windows

Question

I had set a fixed size on my Login window however once you login in and it takes you to the LoadingBar window the size restrictions stay even though I set a new fixed size. This leaves my window with blank area. I have tried looking for similar posts but have not found any. This may have a very simple fix and I may have made a very stupid mistake. I would appreciate any help and an explantion. There is no error when running the code

#IMPORTS
import sys, os, sqlite3
import random, datetime
from PyQt5 import QtCore, QtGui, uic
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5 import QtWidgets #, QtWebEngineWidgets
from PyQt5.QtWidgets import QApplication, QWidget, QPushButton, QMessageBox
import sqlite3
import time 

#WINDOWS
window1 = uic.loadUiType("login.ui")[0] 
window2 = uic.loadUiType("SIGNUP.ui")[0] 
window3 = uic.loadUiType("main.ui")[0] 
window4 = uic.loadUiType("login_loadingbar.ui")[0]
#CLASSES AND MODULES
class Login(QtWidgets.QMainWindow, window1):
    def __init__(self, parent=None):
        QtWidgets.QMainWindow.__init__(self, parent)
        self.setupUi(self)
    
    
    #Set title
    self.setWindowTitle('Login Window')
    self.setFixedWidth(480)
    self.setFixedHeight(620)
        
    self.loginButton.clicked.connect(self.loginfunction)
    self.password_field.setEchoMode(QtWidgets.QLineEdit.Password)
    self.signupHereButton.clicked.connect(self.gotocreate)

    def loginfunction(self):
        username = self.username_field.text() #[email protected]
        password = self.password_field.text() #ptWYccjTQSKX
    
        if len(username) == 0 or len(password) == 0:
            self.login_text.setText("Please input all fields")
     
        else:
            conn = sqlite3.connect("customersSQL.db")
            cur = conn.cursor()
            query = 'SELECT password FROM customer_data WHERE email = \''+username+"\'"
            cur.execute(query)
            result_pass = cur.fetchone()[0]
            if result_pass == password:
                self.login_text.setText("Successfully logged in")
                

            gotoload = LoadingBar()
            widget.addWidget(gotoload)
            widget.setCurrentIndex(widget.currentIndex()+1)
            gotoload.progress()
        else:
            self.login_text.setText("Incorrect username or password")

    def gotocreate(self):
        createacc=CreateAcc()
        widget.addWidget(createacc)
        widget.setCurrentIndex(widget.currentIndex()+1)


class CreateAcc(QtWidgets.QMainWindow, window2):
    def __init__(self, parent=None):
        QtWidgets.QMainWindow.__init__(self, parent)
        self.setupUi(self)
        
        #title
        self.setWindowTitle('Signup Window')
        #Push button
        self.signupButton.clicked.connect(self.createaccfunction)
        self.passwordSignup_field.setEchoMode(QtWidgets.QLineEdit.Password)
        self.confirmPass_field.setEchoMode(QtWidgets.QLineEdit.Password)
        


def createaccfunction(self):
    'This is the create account function where it takes the users input and addes it into the database'
    email = self.usernameSignUp_field.text()
    password = self.confirmPass_field.text()
    if self.passwordSignup_field.text()==self.confirmPass_field.text():
        password=self.passwordSignup_field.text()
        self.signup_text.setText("Successfully created account")
        conn = sqlite3.connect("customersSQL.db")
        cur = conn.cursor()
        #query1 = """INSERT INTO customer_data (email,password)
        #            VALUES(?,?)""", (email,password)
        print (email,password)
   
        cur.execute("""INSERT INTO customer_data (email,password)
                    VALUES(?,?)""", (email,password))
        conn.commit()
        time.sleep(3)
        login=Login()
        widget.addWidget(login)
        widget.setCurrentIndex(widget.currentIndex()+1)
        
class LoadingBar(QtWidgets.QMainWindow, window4): 
        def __init__(self, parent=None):
            QtWidgets.QMainWindow.__init__(self, parent)
            self.setupUi(self)
        
            #title
            self.setWindowTitle('Loading')

        
            self.setWindowFlag(Qt.FramelessWindowHint)
       
            self.setFixedHeight(693)
            self.setFixedWidth(351)
        
   
   
   
   
   
   
   
       #makes progress bar go from 0-100, time scaled

        def progress(self):
            for i in range(100):
                time.sleep(0.1)
                self.login_progressBar.setValue(i)
                QtWidgets.QApplication.processEvents()







class MainWindow(QtWidgets.QMainWindow, window3):
    def __init__(self, parent=None):
            QtWidgets.QMainWindow.__init__(self, parent)
            self.setupUi(self)
        
        

app=QApplication(sys.argv)
w1=Login()
widget=QtWidgets.QStackedWidget()
widget.addWidget(w1)

widget.show()
app.exec_()