Hey, @psoldi👋 Can you post the full request and response for both setting (creating?) the associations and then for the second example where they came back as +1, please? It will be helpful in trying to recreate your steps and give the community a bit more information to work with.
I have kind of the same problem, it is not the same id depending of the request. When I ask for contacts of a company : /crm/v4/objects/company/xxxxxxxxxxxx/associations/contact