Getting SIGTERM is a real curiosity. Ctrl-C sends SIGINT, and the OOM killer sends SIGKILL. SIGTERM is the default signal sent by the kill command, if you don’t specify a different signal.
Looking at the message_bus code, I’m about 99% sure the problem is something to do with the communication being interrupted and the message bus deciding to take its bat and ball and go home. The exception coming out of message_bus shouldn’t happen, either (I’ll do a PR on that), but it’s a side-effect, not the cause. @sam is obviously the go-to guy on what’s going on in the innards, it being his gem.