Slave worker has stopped after at least one previous worker encountered an error when slave-preserve-commit-order was enabled. To preserve commit order, the last transaction executed by this thread has not been committed. When restarting the slave after fixing any failed threads, you should fix this worker as well.
This page shows information specific to MariaDB SkySQL. Information for non-SkySQL use can be found on the ER_SLAVE_WORKER_STOPPED_PREVIOUS_THD_ERROR page in the MariaDB Enterprise Documentation.