The problem is caused by a .001 gap. Go to Storyboard mode to see it. Right-click | DELETE. (The
icons, which never appear between adjacent clips, should have clued me in.) Various transitions will result in a dip or crossfade between the two clips.
If you truly want the FROM clip to fade, and the TO clip to pop on, program a Transparency effect on the FROM clip.

Or, prior to programming the fade, expand the timeline almost fully with the slider at the bottom-right. Drag the TO clips to the right just slightly. Now program the FROM clip fade.

Glad it worked out.