Participants are reporting emails getting sent out duplicate times in the participant center. Under Sent, it lists the single recipient multiple times for one email send.
Participants may see recipients listed multiple times in their email sent history. These emails are only getting sent one time per recipient regardless of the same recipient or recipients listed multiple times. You may need to copy your participant center and upgrade to the most current version.
We are currently evaluating this issue and will update this article when we have more information.