Updated PHP to latest version from 7.3 following WordPress health prompt. This resulted in welshbridgeunion.org displaying website from two days earlier on the machines of some users, whilst others viewed the website with the latest updates. This continued all through 24 hours and I reverted back to PHP 7.3. The problem still persists. DataCentre support say this appears to be a theme issue as it does not occur when using stock WordPress theme. We have had no previous problem with the premium theme.