Python Multiprocessing running process twice?

Running the following Python 3 script and for some reason that I cannot fathom the startWebview function executes twice resulting in two PyWebView windows being opened.

# Import Modules Here
import os
import time
import webview
import os.path
import multiprocessing
from dotenv import load_dotenv
from flask_wtf import FlaskForm
from flask_mde import Mde, MdeField
from wtforms import SubmitField, StringField
from wtforms.validators import InputRequired, DataRequired, Length
from flask import Flask, request, render_template, flash, session, url_for

app = Flask(__name__)
load_dotenv()
mde = Mde(app)
app.config['SECRET_KEY'] = os.environ.get("FLASK_SECRET_KEY")

windowTitle = os.environ.get("WINDOW_TITLE")
fileDirPath = os.environ.get("FILE_DIRECTORY")


def error_flasher(form):
    for field, message_list in form.errors.items():
        for message in message_list:
            flash(form[field].label.text + ': ' + message, 'error')
    print(message, message_list)


def fileHandler(form):
    savePath = os.path.join(fileDirPath, form.title.data)
    f = open(savePath, "w+")
    f.write(form.editor.data)
    f.close()


def contentLoader(form):
    savePath = os.path.join(fileDirPath, form.title.data)
    fileName = savePath
    f = open(fileName, "r")
    return f.read()


class MdeForm(FlaskForm):

    title = StringField('Title', validators=[DataRequired()])

    editor = MdeField(
        validators=[
            #InputRequired("Input required"),
            Length(min=0, max=30000)
        ]
    )
    submit = SubmitField()


@app.route('/', methods=['GET', 'POST'])
def index():
    form = MdeForm()

    if form.validate_on_submit() and form.editor.data == "":
        form.editor.data = contentLoader(form)

    elif form.validate_on_submit() and form.editor.data != "":
        session['editor'] = request.form['editor']
        fileHandler(form)
        form.title.data = ""
        form.editor.data = ""

    return render_template("index.html", form=form, windowTitle=windowTitle)


def startFlaskServer():
    app.run(debug=True)


def startWebview():
    webview.create_window(windowTitle, 'http://localhost:5000')
    webview.start(debug=True)


if __name__ == "__main__":

    p1 = multiprocessing.Process(target=startFlaskServer)
    p2 = multiprocessing.Process(target=startWebview)

    p1.start()
    time.sleep(2)
    p2.start()
    p2.join()
    p1.terminate()

As seen in the above image it would appear that the cause is two GET requests as the second Webview only loads after the second GET request.

Thanks in advance!

It would appear that this issue is caused by Multiprocessing re-evaluating the file as suggested by @Carcigenicate.

Problem solved by moving from Multithreading to threading.