Contacts getting REMOVED from lists

[NilsP48]

I am running a once-daily sync script against your v2 endpoints to create contacts and add existing contacts into lists. I am observing new behavior where the list association changes for unknown reasons. I have numerous contacts which, after my script completes, are part of at least one, in many cases 3 different lists. The account record looks something like this in json:

{
    "id": "1097112912",
    "status": "ACTIVE",
    "confirmed": false,
    "lists": [{
        "id": "1635462118",
        "status": "ACTIVE"
    }, {
        "id": "1436890021",
        "status": "ACTIVE"
    }, {
        "id": "1454185074",
        "status": "ACTIVE"
    }],
    "source": "API",
    "email_addresses": [{
     "...."
    }]
}

When I rerun the script 24 hours later, there are many contacts which are suddenly removed from all lists and have the status "REMOVED". What can cause these automatic list removals with Constant Contact? This happens without any additional API or UI interaction.

Any hint is highly appreciated.

[Courtney_E]

Thank you for reaching out to Constant Contact API Developer Support, and for your patience. My team is here to assist outside software developers with questions about building into Constant Contact's API.

It looks like we've already followed up with you directly via email, but here is the information provided for visibility on the forum:

In this case, it’s most likely that a PUT call was sent to update the contact(s) without including an array of their list memberships in the request body, which would result in removal from all lists.

Resource for contact statuses:  

https://v2.developer.constantcontact.com/docs/contacts-api/contacts-index.html#contact_status  

The details about not including that array are here:  

https://v2.developer.constantcontact.com/docs/contacts-api/contacts-resource.html?method=PUT  

You have to expand the 'lists' property in the Structure section