Several bugs in Galera lead to sporadic failures when testing MariaDB server with the mtr due to false error messages (or warnings) that are not related to the new fixes:
1) Some mtr tests sometimes fails due to
[Warning] WSREP: gcs_caused() returned -1
2) Some mtr tests sometimes fails due to
[Warning] WSREP: Failed to report last committed <number>
3) Some mtr test sometimes fails when node is evicted from the cluster in middle of SST.
4) If SST fails due to a network error, the node that acted as a donor sometimes does not return to its original state, which leads to failure due to the inability to continue the test execution (due to a timeout).