Issue migrating Custom Event Transformer to App with Event Transformer

We are trying to migrate an existing custom event transformer to an App with Event Integration and a custom transformer.

The source of the event is an AWS SNS subscription and we are finding that the initial subscription posts are not creating incidents properly.

If just using the default/demo transformer, an incident is created but there is no content in the “detail”, so we see no subscribe link.

If we change the code at all, we stop getting incidents created at all from the SNS subscribe attempt and no errors with debug enabled.

Manual POSTs to the enqueue endpoint using modified code does appear to work, so it’s not clear what is happening to the SNS post.

Logged a support case, but haven’t had a response after almost 2 weeks, so trying the community instead.