Issue repmgr 5.2.1 switchover postgres 12 on RHEL8 SELinux enforcing

Hi,

I have an issue with postgresql & repmgr on RHEL8.
I have installed postgres 12 and repmgr 5.2.1 on two RHEL8 servers with SELinux in enforcing mode.
The installation went fine and a switchover dry-run seems ok:

          [postgresql@serverb ] $ $/usr/pgsql-12/bin/repmgr standby switchover -f /data/repmgr.conf --dry-run
        NOTICE: checking switchover on node "serverb" (ID: 2) in --dry-run mode
        INFO: SSH connection to host "servera" succeeded
        INFO: able to execute "repmgr" on remote host "servera"
        INFO: 1 walsenders required, 5 available
        INFO: demotion candidate is able to make replication connection to promotion candidate
        INFO: 0 pending archive files
        INFO: replication lag on this standby is 0 seconds
        NOTICE: local node "serverb" (ID: 2) would be promoted to primary; current primary "servera" (ID: 1) would be demoted to standby
        INFO: following shutdown command would be run on node "servera":
          "/usr/pgsql-12/bin/pg_ctl -D $PGDATA stop -m fast"
        INFO: parameter "shutdown_check_timeout" is set to 60 seconds
        INFO: prerequisites for executing STANDBY SWITCHOVER are met

But when I start the switchover I get this:
postgresql@serverb ] $ /usr/pgsql-12/bin/repmgr standby switchover -f /data/repmgr.conf --dry-run
NOTICE: executing switchover on node "serverb" (ID: 2)
NOTICE: local node "serverb" (ID: 2) will be promoted to primary; current primary "servera" (ID: 1) will be demoted to standby
NOTICE: stopping current primary node "servera" (ID: 1)
NOTICE: issuing CHECKPOINT on node "servera" (ID: 1)
DETAIL: executing server command "/usr/pgsql-12/bin/pg_ctl -D $PGDATA stop -m fast"
INFO: checking for primary shutdown; 1 of 60 attempts ("shutdown_check_timeout")
INFO: checking for primary shutdown; 2 of 60 attempts ("shutdown_check_timeout")
...
INFO: checking for primary shutdown; 59 of 60 attempts ("shutdown_check_timeout")
INFO: checking for primary shutdown; 60 of 60 attempts ("shutdown_check_timeout")
ERROR: shutdown of the primary server could not be confirmed
HINT: check the primary server status before performing any further actions

Are there known issues with postgres 12 and repmgr 5.2.1 with RHEL8 and SELINUX in enforcing mode?
Any suggestions on how to proceed with debugging?