Multicamera editing crashing

This is what happens:  I hit the spacebar, then use the number keys to make the edits/switches, then hit the spacebar again to stop playback, and Premiere crashes.  There are no apparent changes in the timeline

I have done this many times before without this problem, though this is the first time since updating to the latest version; that's the only thing I can think of that's different.

The sequence has only two cameras.  The source footage is 3840x2160, but I am using 720p proxies, so playback is generally fine.

As I say, this has worked fine in the past, so I don't believe hardware is relevant.

Any ideas?

(Adobe online help chat was no help!)