Auto track zoom rusted in place?

[Sleetah2000]

Somehow during the course of a project, my autozoom behaved as though it had rusted in place.  As I wrote up the problem, I discovered my own fix (described below).  Can anyone explain what happened here, and why these steps were necessary?  I've attached a skeleton version of the project, for reference.

Thanks

Towards the end of a project, I found that the auto track zoom feature had stopped working  I finished working under this limitation and then made a copy to isolate the problem.  After deleting track by track, I never really determined the source of the problem, but I did figure out the following solution:

1).  When I select track1, it doesn’t expand automatically.

2).  If I select and expand track1, then select track2, track2 does not expand, but track1 returns to minimum height.

3).  By accident, I hit the following resolution.  Select multiple tracks (at least 2).  Expand by dragging any of the selected tracks.  Return these to minimum height.  Select and expand 1 track to desired auto zoom.  Now, when I select any track, auto track zoom works again.

I don’t know whether the problem was triggered by user action, a restart of the DAW, or corrupted data.  I do know that autozoom worked earlier in the project.

No auto zoom.cwb