Resolved
Overview of the issue
Radium One Click Demo Install is a library for importing demo content to WordPress sites.
It is included in a variety of themes and causes the following infinite loop when used together with WPML:
PHP Fatal error: Maximum function nesting level of '100' reached, aborting!
Workaround
The suggested workaround is available on the library’s GitHub page:
https://github.com/FrankM1/radium-one-click-demo-install/issues/33
All you have to do is to edit the file inc/theme-options/importer/importer/radium-importer.php in your theme and wrap the add_filter() with an if statement:
global $pagenow; if ( $pagenow === 'themes.php' ) { add_filter( 'add_post_metadata', array( $this, 'check_previous_meta' ), 10, 5 ); }
Please note that the actual location of the file may vary from theme to theme and the themes that include this library would need to be updated too.