Smarty Compiler Error

I had tried to install OJS but ran into major problems so I had to revert back to the previous version from my back up ((back to OJS 3.1.2).
I am able to get the journal back online however, at the editor/admin level I am unable to access the archive issues/articles and am getting the error below when I click on any old article from the admin/backend.

I have tried removing all plugins and reactivating them without much avail. Any help would be appreciated.

Fatal error : Uncaught → Smarty Compiler: Syntax error in template “app:app:layoutsbackend.tpl” on line 15 “{title|strip_tags value=$pageTitle}” unknown tag ‘title’ ← thrown in lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_templatecompilerbase.php on line 15


Hi @ISER_Editor,

What theme plugin are you using? It looks like an error in a template file which likely origins from customization.