Internal error when editing pages in MediaWiki
If you get an Internal error when trying to edit your pages in MediaWiki, enable debugging by adding the following line at the bottom of the LocalSettings.php file:
$wgShowExceptionDetails = true;
To modify the file use FTP, SSH, or File Manager in Site Tools.
This will give you the exact error message, as well as a backtrace result so that you can see what is causing the problem.
If you get an error message similar to this:
Invalid h node passed to PPNode_DOM::splitHeading
add the following code at the bottom of LocalSettings.php:
$wgParserConf[‘preprocessorClass’] = ‘Preprocessor_Hash’;
This should resolve your issue and you will be able to edit your MediaWiki pages again.