user warning: Not unique table ...

I am getting the following message in the Signup Administration page after I have tried to use Signup module with two different content types with a DATE/TIME field:

user warning: Not unique table/alias: 'content_field_event_date_time' query: SELECT n.nid, n.title, n.type, s.status AS signup_status, COUNT(s_l.nid) AS signup_total, s.close_signup_limit AS signup_close_signup_limit, field_event_date_time_value, field_event_date_time_value FROM node n INNER JOIN signup s ON s.nid = n.nid LEFT JOIN signup_log s_l ON s.nid = s_l.nid LEFT JOIN content_field_event_date_time ON content_field_event_date_time.vid = n.vid LEFT JOIN content_field_event_date_time ON content_field_event_date_time.vid = n.vid GROUP BY n.nid, n.title, signup_status, signup_close_signup_limit ORDER BY n.title ASC LIMIT 0, 25 in /var/www/html/drupal-5.7/includes/database.mysql.inc on line 174.

Everything is fine if I only use one content type but we have different types of workshops so each content type is a different type of workshop.

I've included images so you can see the message and the versions. The module appears to work but I'm trying to clear up the message.

I'm using Drupal 5.16.

If you could include information on how to fix I would prefer that as I've modified the date.5x-2.inc to use the reminder as an evaluation email instead. The change just makes the email sent after instead of before.

Thanks