Bot Tracker is this a bug

WARNING: /var/www/html/piwik/plugins/BotTracker/API.php(73): Deprecated - Function create_function() is deprecated - Matomo 3.6.0


The BotTracker plugin isn’t maintained by the Matomo team, so you should probably report the issue directly to the programmer:

I wouldn’t be surprised, if this has fixed the issue, but there hasn’t been a new release of the plugin since: