The AWS PutCloudWatchMetric processor has a Unit property that requires a value from AWS's CloudWatch API specifications. This value is a constant from a predefined set of string parameters. The API enforces casing so a unit value of "bytes" fails to make a successful API request, whereas "Bytes" succeeds. I've attached a screenshot that leads to a stack trace.
The proposed fix includes a new Validator() to warn the user about the issues prior to starting the PutCloudWatchMetric processor and a set to determine the partitions for the Unit field in API requests to AWS.
This is the hyper link for the API specification details: