We've experienced crash with MariaDB-Galera-5.5.33a last night. Reading the logs it seems that there are a couple different issues (see attached log file from the problem node):

1) There was a long lock wait that caused problems on one of the nodes. However this did not kick out this node from the cluster thus it affected operations for the whole cluster.

2) After the restart the node was not able to recover and died with the following error (and stack trace - see log file):

131020 7:38:12 InnoDB: Assertion failure in thread 47736910333680 in file fsp0fsp.c line 3566
InnoDB: Failing assertion: xdes_get_bit(descr, XDES_FREE_BIT, header_page % FSP_EXTENT_SIZE, mtr) == FALSE