Mariadb 10.2.21 Crash on startup when using mariabackup and galera

We recently upgraded to MariaDB 10.2.21 running on RHEL 7.6

Now, When starting "sudo service mariadb start" and attempting to rejoin the running galera cluster (2 running nodes - this would be the third). The mysqld process crashes. Several seconds later it "retries" and succeeds. In our "production" environment we see the same behavior, except the galera sync using mariabackup is then failing after it spontaneously retries. Right now - im more interested in understanding why the mysqld process is hanging/crashing upon startup though - as it was only a minor update 10.2.20 -> 10.2.21

Complete mysql.log here: https://pastebin.com/GCHUxNR7