Djangoで投稿に成功しない

下記のようなコードで投稿できるプログラムを作ったのですが、このコードで投稿ボタンを押すとform.is_valid()の結果がFalseになっているのかなぜかindexページに飛ばされ投稿ができません。
ターミナルでは普通に"POST /post/new/ HTTP/1.1" 302 0と正常にリダイレクトされたようなのですが何が原因で投稿に失敗するのでしょうか。
詳しい方教えていただけると幸いです。

models.py

django
1from django.db import models
2from django.conf import settings
3from django.utils import timezone
4
5
6class Category(models.Model):
7    COLOR_CHOICES = (
8        ('#D50000','Red'),
9        ('#D94182','Pink'),
10        ('#E36A00','Orange'),
11        ('#F6BF26','Yellow'),
12        ('#0B8043','Green'),
13        ('#258C6D','ForestGreen'),
14        ('#039BE5','Cyan'),
15        ('#1169EB','Blue'),
16        ('#8E24AA','Purple'),
17        ('#AA6402','Brown'),
18        ('#616161','Gray'),
19        ('#000000','Black'),
20        ('#FFFFFF','White'),
21    )
22    color = models.CharField(max_length=100, choices=COLOR_CHOICES)
23    name = models.CharField(max_length=150)
24    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
25    created_at = models.DateTimeField(default=timezone.now)
26
27    def __str__(self):
28        return self.name
29
30class Project(models.Model):
31    title = models.CharField(max_length=255)
32    category = models.ForeignKey(Category, on_delete=models.PROTECT)
33    description = models.CharField(max_length=400,blank=True)
34    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
35    created_at = models.DateTimeField(default=timezone.now)
36
37    def __str__(self):
38        return self.title
39
40class Record(models.Model):
41    project = models.ForeignKey(Project, on_delete=models.PROTECT)
42    time = models.DurationField()
43    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
44    created_at = models.DateTimeField(default=timezone.now)
45
46    def __str__(self):
47        return self.project.title

forms.py

Django
1from django import forms
2from .models import Category, Record, Project
3from django.forms import ModelForm
4
5
6class RecordForm(forms.ModelForm):
7    class Meta:
8        model = Project
9        fields = ("title","category","description","user")
10
11    project = forms.ModelChoiceField(
12        queryset=Project.objects.all(),
13        widget=forms.Select,
14        empty_label=None
15    )
16    time = forms.CharField(label="時間")

views.py

Django
1from django.shortcuts import render, redirect
2from django.views.generic import View
3from .models import Category, Record, Project
4from .forms import RecordForm
5from django.contrib.auth.mixins import LoginRequiredMixin
6
7class IndexView(View):
8    def get(self, request, *args, **kwargs):
9        post_data = Record.objects.order_by('-id')
10        return render(request, 'record/index.html', {
11            'post_data': post_data
12        })
13
14
15
16class CreateRecordView(LoginRequiredMixin ,View):
17    def get(self, request, *args, **kwargs):
18        form = RecordForm(request.POST or None)
19        return render(request, 'record/post_form.html', {
20            'form': form
21        })
22
23    def post(self, request, *args, **kwargs):
24        form = RecordForm(request.POST)
25        if form.is_valid():
26            post = form.save()
27            post.user = request.user
28            post.time = form.cleaned_data['time']
29            post.project = form.cleaned_data['project']
30            post.save()
31            return redirect('new')
32        else :
33            form = RecordForm()
34            return redirect('index')

post_form.html

html
1{% extends 'record/base.html' %}
2{% load widget_tweaks %}
3
4{% block content %}
5<div class="post-form-main">
6
7<div class="post-form">
8<div class="post-form-title">Create a post</div>
9<form method="post">
10    {% csrf_token %}
11    <div>
12        <select id="tag" class="form-control" name="tag">
13            <option hidden>Choose a project</option>
14            {% for project in form.project %}
15            <option value="{{ project }}"></option>
16            {% endfor %}
17        </select>
18        <div class="content-input">{% render_field form.time placeholder="時間"%}</div>
19        <button class="btn" type="submit">Post</button>
20    </div>
21</form>
22</div>
23</div>
24{% endblock %}