OQGraph crashes under load

I've been updating one of my applications from OQGraphv2 to v3 and while initial tests showed everything working, I'm now getting troublesome crashes when I put some load on the OQGraph table.

The application is basically a webservice (in PHP) that queries the OQGraph table (schema attached) and returns the result. The query in itself should be fairly simple:

SELECT db.* FROM db_history AS db INNER JOIN version_history AS v ON db.nodeID = v.linkid WHERE origid = 1 AND destid = 3 AND latch = 'dijkstras';

When doing single sequential requests in the browser, everything works fine. But once I started to put some load on the webservice (using siege as load testing tool), MariaDB crashes quickly after 1-2 requests (crash dump attached), always with the same crash dump.

I should note that the database setup is a master-slave replication setup. I'm not sure that has anything to do with the crashes I'm seeing though.

I can reproduce this fairly easily and reliably in my test environment, on both the slave and the master node, but have not been successful so far in producing a test case that does not involve running siege.