1/ How we found the issue reason -> https://prnt.sc/M9y42BouzdrH 2/ When we deactivated that plugin – search started to work -> https://prnt.sc/pDthVTxTVZTD 3/ We found that this custom code was the main issue -> https://prnt.sc/Pyijd07H1HE0 4/ We improved your code to make it works without errors and also it is minimazed now -> https://prnt.sc/i3VE5mORS71W
You may read articles about wordpress filters/actions to know how to use them correctly https://developer.wordpress.org/reference/functions/apply_filters/ https://developer.wordpress.org/plugins/hooks/filters/ https://developer.wordpress.org/reference/functions/do_action/ https://developer.wordpress.org/reference/functions/add_action/
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