Why are participants receiving their credentials from a previous event?

Participants receive the Message Template from the last events they participated in with that address.

When a participant requests a password from a previous event, the resulting email message is generated from the event(s) they last participated in with that e-mail address.

The message they receive will contain all content specific to that event, including contextual merge fields. Such merge fields will drive to old, and potentially Not Live events.

To prevent users from being driven to erroneous campaigns, it is recommended that merge fields and live links be removed from the Password Request message template of previous /not live events, and copy be generic to the organization -- just in case a user might have multiple addresses or be a superstar that fundraises for multiple of your campaigns.