So, just for kicks I decided to see what would happen if I attacked Lothar with my Patience Missile spell (level 11 variant: repeating ballista). After a few shots he insta-killed me with his powers, but at that moment the game crashed. I think what happened was that either the ballista fired another round the very moment that he killed me or a round impacted him the very moment that he killed me. I got a dump from the crash so I will upload it. A few attempts to repro the crash failed so I don't think I can make a redmine report of this.
This is not the first time the game has crashed on me though. It occasionally crashes at random times, but not very often. The only pattern I have noticed is that several (but not all) of these crashes have happened during area transitions (after creation of the autosave as I was able to reload from it each time). I will include all the dumps I have gotten up to this point in case you would want them, but the dump for the Lothar crash is dated as 2017_4_29.
Edit: I did get the crash to happen again after some further attempts. It seems to happen when he kills you after a bolt gets fired but before it hits him. I have made a report on redmine: http://redmine.beamdog.com/issues/30758