Shutdown of database and stop slave do not work in MariaDB 10.3.17 when slave threads are running

Hi,

I just upgraded a slave of a 10.3.15 from 10.3.15 to 10.3.17. Now I cannot shutdown the database or stop the slave threads, if they are running (I need to use kill -9).

When I start the database with skip_slave_start, I can shutdown the database normally.
When I start only the IO_THREAD or only the SQL_THREAD, stop slave works.
When I start all threads, neither stopping them or shutting down the whole database works.
However, when the master is not reachable when starting the slave threads, stopping them is possible.
When the master is shut down while the slave threads are running, stopping the threads will not work. show slave status shows:

Slave_SQL_Running_State: Waiting for worker threads to be idle

Please let me know if you need further information.

Cheers,
Volker