Hello Justin,
Thank you for reaching out to Constant Contact API Developer Support. My team is here to assist outside software developers with questions about building into Constant Contact's API.
This type of issue wouldn't be related to the version of the API, but rather the types of calls being used to manage the contacts, as there are several different ways to manage contacts via API. Additionally, if more than one integration is connected with an account, they can sometimes work in conflicting ways for the same reason.
If you'd like us to take a look at the account for you, feel free to reach out to our team directly/securely via email at webservices@constantcontact.com and provide the Constant Contact username, integration name, and some examples of lists/contacts that are being affected so that we can better assist you.
As a side note:
While no date is currently set, there will be a point in the near future where our legacy V2 API will begin deprecation. Due to this, while we will continue to deploy critical bug fixes at this time, we will not be doing any more development for V2 or its endpoints, and strongly recommend upgrading to the V3 API to ensure you're ahead of the curve.
Please have a look and let us know if you have any other questions!
... View more
