gcache.size was sufficient enough not to require a SST on the previous upgrades so the problem may be older.
2 node + garb setup running since 10.2.9
Yesterday after a blackout, tried restarting the cluster. 2nd node was damaged bad, so I wiped out the entire datadir in order to do a full SST
initial config was using rsync. tried to do it with mariabackup and xtrabackup-v2
both servers have identical config, except for node names
firewall and selinux both off