Suddenly, "skip selection" playback not working

Summary: I downloaded Audition CC 2017 yesterday (previously, I was using CC 2014). It worked great. Today, after a couple hours of editing in Waveform view, "skip selection" suddenly stopped working.

I am using a late-2015 iMac, 27" with Retina display, 24 MB RAM, 3T fusion drive. Sierra 10.12.1. After my most recent updating of Audition, I am using Audition 2017.0.1 release, build 10.0/1/8

Here's what happens:

1. I make a selection

2. If "skip selection" is not chosen, the selecion plays back properly. (With or without "repeat selection")

3. If "skip selection" IS chosen, when I press the spacebar, I hear a sound, the playback head starts to move (from the beginning of the selection, not from 3 (or however many) seconds before the selection, as it should. The playhead seems to jitter as it moves. And I hear no further sound.

So far, here is what I have tried:

1. Close all other applications

2. Restart iMac

3. Update Audition to the latest version.

4. Check that Core Audio is selected as the playback hardware.

Everything seems to be working fine - unless I choose "Skip selection" and press the spacebar to play.

Any ideas?

Thanks!

Doug