Event Report filter not working
It can be a good idea to clear all CiviCRM caches. You can do that using the url https://www.yourdomain.com/civicrm/menu/rebuild.

Regarding the logs, you can turn on logging and debugging in CiviCRM (https://www.yourdomain.com/civicrm/admin/setting/debug?reset=1) and then have a look at the log available in Drupal's UI first: https://www.yourdomain.com/admin/reports/dblog