Have you been able to resolve the issue? As Kane noted, we’ve seen this come up in the past when webhooks are enabled on Patreon that Discourse isn’t configured to handle. You need to be sure to only enable the webhooks that are shown in the second screenshot of this section of https://meta.discourse.org/t/configuring-patreon-integration-with-discourse/62380#configuring-the-optional-patreon-webhook. Those are the first three webhooks in the screenshot.
Let us know if this doesn’t resolve the issue for you.