This error is thrown when debezium connector is trying to unregister a MBean that is never registered when stopping a debezium engine.

And according to both 

https://github.com/debezium/debezium/pull/665/files/901787664c3941201d4ba28f18e39b3d4325b3ee#diff-04b0dbf3706a1ff811bc729448f0cfb3R67

and our product logging, the failing to register exception is logged as a warning while the failing to unregister exception is still an error. Will appreciate if these behaviors are consistent on both side.

More info:

https://gitter.im/debezium/user?at=5f34232a3cf046461e2eb0be