If you are having an Error When Saving Theme Options, you have a Server Error 500, Server Error 404, Server Error 403, or you’re addressing an empty page, here’s a list of possible causes we’ve been collecting over time.
As you can see the problems are always related to hosting resources that interrupt the saving of the options.
Please understand that Unicode is a super-tested and trusted product. If something, as important as the Theme Options, does not work (and only in your installation), the problem is to be evaluated in some server-side settings.
Firstly, we encourage you to ask your host support why produce an error on this server and ask to verify the specific error information they can read in the Error Log file.
Error When Saving Theme Options – Memory Limit
If you save Theme Options and you have an error please verify that you don’t have any red messages inside your System Status related to Memory Limit. The WP Memory Limit is the maximum amount of memory (RAM) that your site can use at one time.
You generally have a Memory Limit issue when your installation is not compliant with the Server Requirements for a modern WordPress installation.
If you save Theme Options and you have an error please try to deactivate all your extra plugins to check if this fixes the issue. For example, a few users had performance issues with extra plugins.
If you save Theme Options and you have an error this can be related to an out-of-date version of PHP, please verify that your host is offering you the latest and official suggested by WordPress which is PHP 7+.
Some hosts limit your resources. When you save Theme Options you compile some actions at the same time and they do not permit you to do this. Please ask them to review these settings for you.
This is the reply from a collaborative host:
Yes, it seems that you triggered one of our security measures called Mod Security. It appears that the delete function is causing multiple backend calls simultaneously, which is causing the system to malfunction. However, we have disabled this rule since it only applies to the admin area, so there should be no increase in the risk of any account exploits.
Pattern match (ModSecurity)
A user reported the problem was a pattern match blocked by the host:
Request: POST /wp-admin/options.php Action Description: Access denied with code 403 (phase 2). Justification: Pattern match "(?i)([\s\"'`;\/0-9\=\x0B\x09\x0C\x3B\x2C\x28\x3B]+on\w+[\s\x0B\x09\x0C\x3B\x2C\x28\x3B]*?=)" at ARGS:_uncode_post_custom_fields_settings_array.
The easy solution is to go to Cpanel — ModSecurity – Deactivate