Error creating Blog Post via API


We are trying to create a blog post via the Blog API.

We are using OAuth2 API, and we have the permissions for Files and Content. However, when trying to create a Blog Post, we receive the following error message :

This is very confusing, as we can create a page perfectly well, except for the Auto-save buffer issue I’ve opened a separate topic for. The ID you see in the screenshot is dynamically changing everytime we repreat the request. We have also tried to get the blog post by the id we get in the error message above, for multiple instances, and we receive a NULL result for every single one of them. So this seems to really be a permission issue. We can create a post manually using the same user we have installed the integration with, so no issue with the ACTUAL USER permissions as well.

Any help is much appreciated as this is quite an urgent issue which is stopping our progress in tracks.

Thanks in advance.