Error handling with checkpoint and bisect on batch retries do not work

[SilverSpirit]

For the extra credit part of the workshop, specifically https://data-processing.serverlessworkshops.io/stream-processing/05-extra-credit/05-01-eh-cp-bb.html the provided lambda code does not work. The lambda executes once and no retries occur. The earlier section with just bisection works and I can see the calls made to the lambda and the records written to DDB. I am not certain, but it might be due to the place where batchItemFailures is being returned (i.e. not in the main handler).