Challenge 2: An Unexpected Cascading Shift After Trimming — Solution Walkthrough

What likely happened:

Per this chapter's own warning box, the editor was very likely working
in Ripple mode without realizing it. Ripple edit trims a clip's own
edge and automatically shifts every subsequent clip on the track to
close the resulting gap — exactly matching the described symptom of
every later clip unexpectedly moving earlier after a single trim.

Why this happened despite the editor expecting only one clip to
change:

Per this chapter's own material, this is precisely the surprise
Ripple's own automatic gap-closing behavior can cause — a genuinely
powerful feature for maintaining a tight edit with no gaps, but one
that produces an unwanted cascading shift if the editor didn't
actually intend for later clips to move. The editor assumed trimming
worked the way a simpler, non-rippling trim would, without realizing
which mode was currently active.

The fix going forward:

Per this chapter's own material, checking which trim mode is active
before trimming avoids this exact surprise — if only the single clip
being trimmed should change, switching out of Ripple mode first
(or undoing this trim and retrying with a different trim mode) would
produce the originally expected result.

WHY THIS WORKS AS AN ANSWER
------------------------------
This exercise directly applies this chapter's own warning box to the
exact symptom it describes, correctly identifying Ripple mode as the
cause and recommending the same preventive habit the chapter
recommends.