Perch Blog -403 Forbidden error

Hi, A client has advised that they are unable to copy/paste in a YouTube video source to the Redactor window on their Perch Blog. When I try to do so, I get this error:

Forbidden
You don't have permission to access /perch/addons/apps/perch_blog/edit/ on this server.
Additionally, a 403 Forbidden error was encountered while trying to use an ErrorDocument to handle the request.

I know this functionality works as I have used it in the past. I tried to give that specific folder full write access, but that actually broke blog posts completely, so I had to revert. Any ideas why this is happening?

Debug on page

Debug Message - Perch 3.0.12
[1] SELECT u.*, r.* FROM perch3_users u, perch3_user_roles r WHERE u.roleID=r.roleID AND u.userEnabled=1 AND u.userID=2 AND u.userHash='320f8bc7ace71bcd30b25a9529f8f59c' LIMIT 1
UPDATE perch3_users SET userHash='77c8aac83dbaab2a2d09f25df124728f' WHERE userID='2'
[31] SELECT settingID, settingValue, userID FROM perch3_settings WHERE userID=2 OR userID=0 ORDER BY userID ASC
[7] SELECT itemValue FROM perch3_menu_items WHERE itemType='app'
[0] SELECT COUNT(*) FROM perch3_blog_comments WHERE commentStatus='PENDING'
[1] SELECT * FROM perch3_blog_authors WHERE authorEmail='james@mckevittarchitects.ie' LIMIT 1
[1] SELECT * FROM perch3_blog_posts WHERE postID=24
[1] SELECT * FROM perch3_blog_sections ORDER BY sectionTitle ASC
[1] SELECT * FROM perch3_blogs ORDER BY blogTitle ASC
[1] SELECT * FROM perch3_blogs WHERE blogID=1 LIMIT 1
[1] SELECT * FROM perch3_blog_sections WHERE blogID='1' ORDER BY sectionTitle ASC
Using template: /templates/blog/post.html
Edit mode: edit
[1] SELECT mi.*, p.privKey FROM perch3_menu_items mi LEFT JOIN perch3_user_privileges p ON mi.privID=p.privID WHERE mi.itemActive=1 AND mi.parentID=0 ORDER BY itemOrder ASC LIMIT 0, 1
[2] SELECT mi.*, p.privKey FROM perch3_menu_items mi LEFT JOIN perch3_user_privileges p ON mi.privID=p.privID WHERE mi.itemActive=1 AND mi.parentID=1 ORDER BY mi.itemOrder ASC
[1] SELECT itemTitle FROM perch3_menu_items WHERE itemType='app' AND itemValue='perch_blog' LIMIT 1
[1] SELECT mi.*, p.privKey FROM perch3_menu_items mi LEFT JOIN perch3_user_privileges p ON mi.privID=p.privID WHERE mi.itemActive=1 AND mi.parentID=0 ORDER BY itemOrder ASC LIMIT 1, 10
[2] SELECT mi.*, p.privKey FROM perch3_menu_items mi LEFT JOIN perch3_user_privileges p ON mi.privID=p.privID WHERE mi.itemActive=1 AND mi.parentID=2 ORDER BY mi.itemOrder ASC
File: /addons/apps/perch_blog/modes/edit.post.php
[1] SELECT * FROM perch3_resources WHERE resourceID='1427' LIMIT 1
Array
(
    [w] => 1000
    [h] => 666
    [target_w] => 1000
    [target_h] => 800
    [crop] => 
    [density] => 1
    [path] => scarlet-street-w1000h800-1-w1000h800.jpg
    [size] => 287064
    [mime] => 
    [assetID] => 1429
)
[nil] SELECT * FROM perch3_categories c, perch3_category_sets s WHERE c.setID=s.setID AND s.setSlug='blog' ORDER BY catTreePosition ASC
Queries: 19
Memory: 2.1652

Diagnostics

Perch: 3.1.1, PHP: 5.6.35, MySQL: mysqlnd 5.0.11-dev - 20120503 - $Id: 76b08b24596e12d4553bd41fc93cccd5bac2fe7a $, with PDO
Server OS: Linux, cgi-fcgi
Installed apps: content (3.1.1), assets (3.1.1), categories (3.1.1), perch_blog (5.5.1)
App runtimes: <?php $apps_list = array( 'content', 'categories', 'perch_blog', );
PERCH_LOGINPATH: /perch
PERCH_PATH: /home/mckevit1/public_html/perch
PERCH_CORE: /home/mckevit1/public_html/perch/core
PERCH_RESFILEPATH: /home/mckevit1/public_html/perch/resources
Image manipulation: GD
PHP limits: Max upload 1000M, Max POST 1000M, Memory: 256M, Total max file upload: 256M
F1: 3b606135b33e6a102526838f4152a807
Resource folder writeable: Yes
DOCUMENT_ROOT: /home/mckevit1/public_html
HTTP_HOST: www.mckevittarchitects.ie
REQUEST_URI: /perch/core/settings/diagnostics/
SCRIPT_NAME: /perch/core/settings/diagnostics/index.php