I’m assuming you are running batch pipeline. If so, the events are likely to be rejected at enrichment due to not validating against your JSON schema. After all, it’s a custom event and you might not have implemented it right. The rejected events would end up in your “bad” bucket.
We recommend using Athena to debug the “bad” events as per Debugging bad rows in Athena [tutorial]. If it’s too complicated you can even examine your “bad” bucket manually but it’s more tedious.