Drupal 8 fatal error:Call to undefined function DrupalfilePluginFieldFieldTypefile_default_scheme() on front page

Hello,

I have been trying to resolve this problem – ‘Fatal error: Call to undefined function DrupalfilePluginFieldFieldTypefile_default_scheme() in
home/firstbz/public_html/core/modules/file/src/Plugin/Field/FieldType/FileItem.php on line 39.
I have a D8 install and using an Omni-drupal theme. Incidentally the error displays on most other browser on clicking the links to frontpage but not other pages (without slider). Recently updated core installation to 8.32 so wonder if this is a factor. Waiting for other ideas before making major changes.
As a ‘newbie’ realise I may be missing something. No indication of plugin module issues as far as I know.
Any help would be appreciated.

Drupal version: 


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