Crash closing certain scores

I see crashes closing certain files. Some seem random, others reproducible. Seems to usually be in the destructor for System, but in different places from there (SpannerSegment and SkylineSegment are "popular"). Here's a couple that crash for me every time:

1) open attached score (say "yes" to reset positions, if asked)
2) close it (say "no" to save, if asked)

The scores that crash seem mostly 2.x scores, but the problem remains if I save in 3.0, close (let it crash), then repeat the experiment using the 3.0 version.