Looks like this may have been caused when auto stretch was on. I was able to intermittently create a crash due to Auto Stretch but it took some work to make happen. This only showed up with the actual STL connected. I ran through over 200 frames with the STL without issue. I'm running another, much larger, set and will check on them in the morning. If you'd like to see if you can duplicate I've released .17 with this change.
http://mainsequencesoftware.com/Releases
Thanks,
Jared