MTR test galera_bf_abort fails with --ps-protocol:

galera.galera_bf_abort 'innodb'          [ fail ]

        Test ended at 2020-11-20 09:06:45

CURRENT_TEST: galera.galera_bf_abort

mysqltest: At line 26: query 'INSERT INTO t1 VALUES (2, 'node_2')' succeeded - should have failed with errno 1213... 

With --ps-protocol certain commands are not expected to return errors (for example COM_STMT_CLOSE). In such a case, the server should keep the error until a subsequent interaction with the client allows the error to be returned.