Pixel 9 - Unable to Use Custom Classes on Blocks with Custom Design Templates

Using the Pixel 9 Theme, when I go to Design and Custom Template on a Feature Block, I add custom Classes such as “fbox:layout:bordered” & “fbox:plain”, but when I go to save, these changes do not save.

Concrete Version

Core Version - 9.2.8
Version Installed - 9.2.8
Database Version - 20240122172319

Environment

production

Database Information

Version: 8.0.36
SQL Mode: NO_ENGINE_SUBSTITUTION
Character Set: utf8mb4
Collation: utf8mb4_unicode_ci

Concrete Packages

Pixel Theme (9.2.2)

Concrete Overrides

None

Concrete Cache Settings

Block Cache - Off
Overrides Cache - Off
Full Page Caching - Off
Full Page Cache Lifetime - Every 6 hours (default setting).

Database Entities Settings

Doctrine Development Mode - Off

Server Software

Apache

Server API

cgi-fcgi

PHP Version

7.4.33

PHP Extensions

bcmath, bz2, calendar, cgi-fcgi, Core, ctype, curl, date, dba, dom, exif, fileinfo, filter, ftp, gd, gettext, gmp, hash, iconv, imagick, imap, intl, json, ldap, libxml, mbstring, mysqli, mysqlnd, odbc, openssl, pcntl, pcre, PDFlib, PDO, pdo_mysql, pdo_pgsql, pdo_sqlite, pgsql, Phar, posix, pspell, Reflection, session, SimpleXML, soap, sockets, sodium, SPL, sqlite3, standard, sysvmsg, sysvsem, sysvshm, tidy, tokenizer, xml, xmlreader, xmlrpc, xmlwriter, xsl, zip, zlib

PHP Settings

max_execution_time - 30
log_errors_max_len - 1024
max_file_uploads - 25
max_input_nesting_level - 64
max_input_time - 60
max_input_vars - 1000
memory_limit - 128M
post_max_size - 50M
upload_max_filesize - 50M
ldap.max_links - Unlimited
mbstring.regex_retry_limit - 1000000
mbstring.regex_stack_limit - 100000
mysqli.max_links - Unlimited
mysqli.max_persistent - Unlimited
odbc.max_links - Unlimited
odbc.max_persistent - Unlimited
pcre.backtrack_limit - 1000000
pcre.recursion_limit - 100000
pgsql.max_links - Unlimited
pgsql.max_persistent - Unlimited
session.cache_limiter - no value
session.gc_maxlifetime - 7200
soap.wsdl_cache_limit - 5
unserialize_max_depth - 4096

This would probably be better as a support ticket for the them theme Pixel 9 :: Concrete CMS Marketplace

Or if you DM directly @shahroq who is the theme developer.