In most cases, if your contact received the same message multiple times, it's not a bug, it is because they entered a campaign workflow multiple times.
How could this happen?
In 99% of cases, if a contact entered multiple campaign workflows, it is because that contact was moved from one list to another one or more times, and the lists they were added to were used as input for different campaigns, or for the same campaign.
In other words, when a contact is moved from one list to another, and those lists are used as campaign inputs, the contact may re-enter a workflow they had already gone through, or enter a new one.
This is what explains why the same contact may receive multiple invitations or multiple identical messages.
How to check this
Open the profile of the contact concerned.
Scroll down to the Analytics Log section.
Check whether you can see:
multiple invitation requests;
multiple sent messages;
and/or list changes.
If these elements appear in the contact’s history, this confirms that there is no bug and that the contact entered a campaign workflow multiple times.
How to avoid this
If you move contacts from one list to another, keep in mind that a contact who has already received a message from a previous workflow will also receive all the following messages from the new workflow they enter.
So before moving contacts to a new list, make sure they have not already received messages.
You can check this by filtering contacts by workflow step in your list.
When to contact support
If you do not see any list change in the logs, and nothing explains why the contact entered the workflow multiple times, then it may be a technical issue.
In that case, please contact support so our team can investigate further.