rpl.parallel_backup* tests sometimes fail with Result length mismatch

rpl.parallel_backup_lsu_off 'innodb,mix' w14 [ fail ]

        Test ended at 2023-02-16 09:31:38

CURRENT_TEST: rpl.parallel_backup_lsu_off

--- /home/buildbot/amd64-ubuntu-2004-fulltest/build/mysql-test/suite/rpl/r/parallel_backup_lsu_off.result	2023-02-16 08:50:33.000000000 +0000

+++ /home/buildbot/amd64-ubuntu-2004-fulltest/build/mysql-test/suite/rpl/r/parallel_backup_lsu_off.reject	2023-02-16 09:31:37.703046027 +0000

@@ -187,6 +187,18 @@

 BACKUP STAGE START;

 BACKUP STAGE BLOCK_COMMIT;

 connection aux_slave;

+Timeout in wait_condition.inc for SELECT COUNT(*) = 0 FROM information_schema.processlist WHERE state = "Waiting for prior transaction to commit"

+Id	User	Host	db	Command	Time	State	Info	Progress

+5	root	localhost:56620	test	Sleep	36		NULL	0.000

+6	root	localhost:56626	test	Sleep	37		NULL	0.000

+9	root	localhost:56628	test	Sleep	32		NULL	0.000

+10	root	localhost:56636	test	Sleep	36		NULL	0.000

+11	root	localhost:56640	test	Execute	0	starting	show full processlist	0.000

+16	root	localhost:56656	test	Sleep	32		NULL	0.000

+33	system user		NULL	Slave_IO	32	Waiting for master to send event	NULL	0.000

+35	system user		NULL	Slave_worker	32	Waiting for backup lock	NULL	0.000

+36	system user		test	Slave_worker	32	Waiting for prior transaction to commit	XA COMMIT X'31',X'',1	0.000

+34	system user		NULL	Slave_SQL	32	Slave has read all relay log; waiting for more updates	NULL	0.000

 ROLLBACK;

 connection backup_slave;

 BACKUP STAGE END;

mysqltest: Result length mismatch