Fatal error on blog post

Morning,

We updated a customers blog yesterday and now on saving block posts we get the following error:

Fatal error: Call to a member function return_instance() on boolean in /~/admin/core/lib/api/PerchAPI_Form.class.php on line 430

I've found this on another forum thread and tried running Perch blog update, which updated the posts but didn't fix the problem. Unfortunately the blog has quite a few posts so I couldn't dump the tables and start again. A full diagnostic is below:

Perch: 2.8.32
Production mode: (PERCH_DEVELOPMENT)
Installed apps: content (2.8.32), assets (2.8.32), categories (2.8.32), perch_blog (4.5.2), perch_forms (1.8.2), perch_twitter (3.3.1)
DB driver: PDO
DB tables: perch2_blog_authors (3), perch2_blog_categories (6), perch2_blog_comments (0), perch2_blog_index (2980), perch2_blog_posts (148), perch2_blog_posts_to_categories (158), perch2_blog_posts_to_tags (157), perch2_blog_sections (1), perch2_blog_tags (85), perch2_categories (6), perch2_category_counts (6), perch2_category_sets (1), perch2_content_index (2912), perch2_content_items (871), perch2_content_regions (95), perch2_forms (3), perch2_forms_responses (141), perch2_navigation (1), perch2_navigation_pages (5), perch2_page_templates (4), perch2_pages (26), perch2_resource_log (1724), perch2_resource_tags (10), perch2_resources (486), perch2_resources_to_tags (14), perch2_scheduled_tasks (20), perch2_settings (30), perch2_twitter_settings (1), perch2_twitter_tweets (775), perch2_user_passwords (0), perch2_user_privileges (40), perch2_user_role_privileges (19), perch2_user_roles (3), perch2_users (6)
Users: 6
App runtimes:
<?php
    include(PERCH_PATH.'/core/apps/content/runtime.php');
    include(PERCH_PATH.'/core/apps/categories/runtime.php');
    include(PERCH_PATH.'/addons/apps/perch_twitter/runtime.php');
    include(PERCH_PATH.'/addons/apps/perch_forms/runtime.php');
    include(PERCH_PATH.'/addons/apps/perch_blog/runtime.php');
?>
Scheduled tasks for perch_blog: delete_spam_comments (1440 mins)
Scheduled tasks for perch_twitter: update_tweets (10 mins)
Editor plug-ins: markitup, redactor
H1: 7f7ced602ea106e2cba988cefe952b69
L1: 41bef620340d2231edc6f493186f89ed
F1: 2edba60ed1f613d6dd804feb202456a2
headerColour: #b01138
content_singlePageEdit: 1
helpURL: https://www.batebrand.com
siteURL: https://maylarch.co.uk
hideBranding: 1
content_collapseList: 1
lang: en-gb
update_2.3.2: done
latest_version: 2.8.15
headerScheme: dark
dashboard: 1
content_hideNonEditableRegions: 1
logoPath: /admin/resources/perch-logo.png
perch_twitter_update: 3.2
update_2.3.3: done
perch_blog_post_url: /news/post.php?s={postSlug}
perch_blog_update: 5.0
perch_blog_slug_format: %Y-%m-%d-{postTitle}
perch_blog_akismet_key:
perch_blog_max_spam_days: 0
perch_blog_comment_notify: 0
on_sale_version: 2.8.32
update_2.4.9: done
update_2.7.2: done
update_2.7.4: done
update_2.8.32: done
PERCH_DEVELOPMENT: 10
PERCH_STAGING: 50
PERCH_PRODUCTION: 100
PERCH_DB_USERNAME: root
PERCH_DB_SERVER: localhost
PERCH_DB_DATABASE: mel_perch
PERCH_DB_PREFIX: perch2_
PERCH_DEBUG: 1
PERCH_PRODUCTION_MODE: PERCH_DEVELOPMENT
PERCH_SCHEDULE_SECRET: Ginger_Beer
PERCH_TZ: UTC
PERCH_EMAIL_FROM: lea.chapman@batebrand.com
PERCH_EMAIL_FROM_NAME: Lea Chapman
PERCH_LOGINPATH: /admin
PERCH_PATH: /Users/lea/Repositories/Maylarch/Maylarch-Core-Site/admin
PERCH_CORE: /Users/lea/Repositories/Maylarch/Maylarch-Core-Site/admin/core
PERCH_RESFILEPATH: /Users/lea/Repositories/Maylarch/Maylarch-Core-Site/admin/resources
PERCH_RESPATH: /admin/resources
PERCH_HTML5: 1
PERCH_RUNWAY:
PERCH_ERROR_MODE: DIE
PERCH_DATE_LONG: %d %B %Y
PERCH_DATE_SHORT: %d %b %Y
PERCH_TIME_SHORT: %H:%M
PERCH_TIME_LONG: %H:%M:%S
PERCH_RUNWAY_ROUTED:
PERCH_STRONG_PASSWORDS:
PERCH_PREVIEW_ARG: preview
PERCH_TEMPLATE_PATH: /Users/lea/Repositories/Maylarch/Maylarch-Core-Site/admin/templates
PERCH_DEFAULT_DOC: index.php
PERCH_DEFAULT_EXT: .php
PERCH_RWD:
PERCH_HTML_ENTITIES:
PERCH_SSL:
PERCH_STRIPSLASHES:
PERCH_PROGRESSIVE_FLUSH: 1
PERCH_PARANOID:
PERCH_FORCE_SECURE_COOKIES:
PERCH_PASSWORD_MIN_LENGTH: 6
PERCH_MAX_FAILED_LOGINS: 10
PERCH_AUTH_LOCKOUT_DURATION: 1 HOUR
PERCH_VERIFY_UPLOADS:
PERCH_AUTH_PLUGIN:
PERCH_DB_CHARSET: utf8
PERCH_DB_PORT:
PERCH_DB_SOCKET:
PERCH_SESSION_TIMEOUT_MINS: 20
PERCH_APPS_EDITOR_PLUGIN: markitup
PERCH_APPS_EDITOR_MARKUP_LANGUAGE: textile
HOSTING SETTINGS

PHP: 5.6.25
Zend: 2.6.0
OS: Darwin
SAPI: apache2handler
Safe mode: not detected
MySQL client: mysqlnd 5.0.11-dev - 20120503 - $Id: 76b08b24596e12d4553bd41fc93cccd5bac2fe7a $
MySQL server: 5.6.28
Free disk space: 434.00 GB
Extensions: Core, date, ereg, libxml, openssl, pcre, sqlite3, zlib, bcmath, bz2, calendar, ctype, curl, dom, hash, fileinfo, filter, ftp, gd, SPL, iconv, intl, json, ldap, mbstring, session, standard, mysqlnd, mysqli, PDO, pdo_mysql, pdo_sqlite, Phar, posix, Reflection, mysql, SimpleXML, soap, sockets, exif, tokenizer, wddx, xml, xmlreader, xmlwriter, xsl, zip, apache2handler, imap, gettext, mcrypt, pgsql, pdo_pgsql, mhash
GD: Yes
ImageMagick: No
PHP max upload size: 32M
PHP max form post size: 32M
PHP memory limit: 128M
Total max uploadable file size: 32M
Resource folder writeable: Yes
Session timeout: 24 minutes
Native JSON: Yes
Filter functions: Yes
Transliteration functions: Yes
HTTP_HOST: maylarch.local
HTTP_COOKIE: PHPSESSID=57546f516ce3df27b6aa897b3d616192; cmsa=1; cookiebar=hide
HTTP_CONNECTION: keep-alive
HTTP_UPGRADE_INSECURE_REQUESTS: 1
HTTP_ACCEPT: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
HTTP_USER_AGENT: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12) AppleWebKit/602.1.50 (KHTML, like Gecko) Version/10.0 Safari/602.1.50
HTTP_REFERER: https://maylarch.local/admin/core/settings/diagnostics/
HTTP_ACCEPT_LANGUAGE: en-gb
HTTP_ACCEPT_ENCODING: gzip, deflate
PATH: /usr/bin:/bin:/usr/sbin:/sbin
SERVER_SOFTWARE: Apache
SERVER_NAME: maylarch.local
SERVER_ADDR: ::1
SERVER_PORT: 80
REMOTE_ADDR: ::1
DOCUMENT_ROOT: /Users/lea/Repositories/Maylarch/Maylarch-Core-Site
SERVER_ADMIN: you@example.com
SCRIPT_FILENAME: /Users/lea/Repositories/Maylarch/Maylarch-Core-Site/admin/core/settings/diagnostics/index.php
REMOTE_PORT: 51082
GATEWAY_INTERFACE: CGI/1.1
SERVER_PROTOCOL: HTTP/1.1
REQUEST_METHOD: GET
QUERY_STRING: extended
REQUEST_URI: /admin/core/settings/diagnostics/?extended
SCRIPT_NAME: /admin/core/settings/diagnostics/index.php
PHP_SELF: /admin/core/settings/diagnostics/index.php
REQUEST_TIME_FLOAT: 1476265177.79
REQUEST_TIME: 1476265177
argc: 1

At the moment the blog posts are displaying but we can't edit or update them so your help would be appreciated.

Thanks, Lea.