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I'd suspect you didn't actually update CiviCRM, as far as CiviCRM is concerned.


Perhaps the old code is still kicking around and accessible to your CMS (e.g. perhaps you left it in, maybe renamed?).
Perhaps you have a very aggressive opcache that hasn't recognized the new code yet.
Perhaps you didn't install the new CiviCRM codebase that you thought you did (I've done that before often enough ...).