mod_proxy_cluster with httpd: pthread_mutex_lock.c:94: ___pthread_mutex_lock: Assertion `mutex->__data.__owner == 0' failed.

When load testing mod_proxy_cluster you might get:
httpd: pthread_mutex_lock.c:94: __pthread_mutex_lock: Assertion `mutex->data._owner == 0' failed.
[Tue Aug 02 16:17:37.674080 2022] [core:notice] [pid 2525150:tid 139785983876032] AH00051: child pid 2525156 exit signal Abort (6), possible coredump in /home/jfclere/APACHE-2.4.x