When a chain of transformations (SMTs) that mutate a record's topic-partition is applied, then Connect is unable to map the transformed record to its original topic-partition. This affects committing offsets.
Currently, in order to reproduce the issue one could use the TimestampRouter transformation with a sink connector such as the FileStreamSinkConnector.
In this ticket we'll address the issue for connectors that don't manage/commit their offsets themselves. For the connectors that do such management, broader API changes are required to supply the connectors with the necessary information that will allow them to map a transformed record to the original.