galera.galera_sst_mariabackup fails with "Failed to start mysqld.2"

It always fails with:
Failed to start mysqld.2
mysqltest failed but provided no output
14:23
In the mysqld.2.error log:
2020-05-13 14:15:54 0 [ERROR] WSREP: Failed to read uuid:seqno and wsrep_gtid_do
main_id from joiner script.
2020-05-13 14:15:54 3 [Note] WSREP: SST received
2020-05-13 14:15:54 3 [Note] WSREP: SST received: 00000000-0000-0000-0000-000000
000000:-1
2020-05-13 14:15:54 2 [ERROR] WSREP: Application received wrong state:
Received: 00000000-0000-0000-0000-000000000000
Required: df55f3aa-950a-11ea-8831-0a0b0fb93391