400 Bad Request from /api/oauth2/api/campaigns/123/pledges

In the last 24 hours, Patreon has consistently began emitting 400 Bad Request responses for API requests to https://www.patreon.com/api/oauth2/api/campaigns/123/pledges?include=patron.null,reward.null&page%5Bcount%5D=1000. The code has not changed. Remove the query string does not change anything.

This is not an authorization issue, because in that case the response is 401. Something has changed at Patreon in the last 24 hours.