No, still nothing.
I've narrowed it down though. It always happens during playback or scrubbing. It does not matter whether the timeline has already been rendered, scrubbing/playing will eventually result in a lockup. And in some rare cases, it will lock up when starting to render the timeline.
It feels like it could be related to having Lightroom open at the same time. But I was only able to work through about two crash cycles last time and I couldn't get a consistent result to say for sure.