Some Publishers Cannot Be Blocked In API

We noticed a strange issue where there are many publisher IDs that cannot seem to be blocked using the API.

We get a successful response (200) to our campaign update request, and in the response object the 'publisher_targeting' seems accurate. However, if we retrieve the campaign details immediately after, the 'publisher_targeting' is missing many (but not all) of the publisher IDs we tried to block. The UI also does not show these publishers as blocked.